EMAIL 094: WEEK12M: Describe the energy transformations that occur when an athelete in pole vaulting. describe the energy transformations that occur during the operation of an automobile.

EMAIL 095: WEEK12M: Explain how energy and force are related. Is it possible to exert a forceand not have a change in kinetic energy?

EMAIL 096: WEEK12M: Explain the difference between kinetic and potential energy. Give formulas for (a) kinetic energy, (b) gravitational potential energy near the surface of the earth and (c) spring elastic energy

EMAIL 097: WEEK12M: A 1600 kg car travels at a speed of 12.5 m/s. (a) What is its kinetic energy? (b) The car drives up a 1200 m high mountain, while maintaining speed. Calculate its kinetic and potential energy.

EMAIL 098: WEEK12M: A 15.0 kg cart is moving with a velocity of 7.50 m/s down a level hallway. After 6.00 m, it slows down to 3.20 m/s. (a) What is the change in kinetic energy of the cart? (b) What happened to its lost kinetic energy?

EMAIL 099: WEEK12T: Bungee Laboratory

EMAIL 100: WEEK12F: Can a baseball have a kinetic energy and a potential energy at the same time?

EMAIL 101: WEEK12F: You ride a bicycle. In what sense is it correct to say that your bicycle is solar powered?

EMAIL 102: WEEK12F: A skier prepares to take off down a snow-covered hill. Is it correct to say that gravity provides the energy for the trip down the hill?

EMAIL 103: WEEK12F: A 20 kg rock is at the edge of a 100 m high cliff. (a) What is its potential enegy relative to the base of the cliff? (b) The rock falls from the cliff. What is its kinetic energy just before impact? (c) What speed does the rock have just before it hits the ground?

EMAIL 104: WEEK12F: A bungee cord has a spring constant of 10.5 N/m and an unstretched length of 20 m. If a 55 kg person attached to the cord, jumps off a bridge, how far will they fall?

EMAIL 089: WEEK11F: Define work and Power. Explain what units are used to measure work and power.

EMAIL 090: WEEK11F: A satellite orbits Earth in a circular orbit. Does the Earth’s gravity do any work on the satellite? Explain your answer.

EMAIL 091: WEEK11F: Sketch 3 machines and identify the Applied (A) and Resistance (R) forces for each machine.

EMAIL 092: WEEK11F: The third floor of a house is 8.0 m above street level. How much work is needed to move a 1500 kg refrigerator to the third floor?

EMAIL 093: WEEK11F: Karen has a mass of 57.0 kg and she rides the up escalator at the Woodley Park Station of the Washington DC Metro. Karen rode a distance of 65 m. How much work did the escalator do on Karen if it has an inclination of 30 degrees?

EMAIL 080: WEEK10M: Jenny has a mass of 35.6 kg and her skateboard has a mass of 1.3 kg. What is the momentum of Jenny and her skateboard together is they both have a velocity of 9.50 m/s northward?

EMAIL 081: WEEK10M: Car "A" has a mass of 1500 kg and travels at a velocity of 30 m/s eastward. Car "B" has a mass 2000 kg and it travels at a velocity of 25.0 m/s at 30 degrees south of west. What is the total momentum of the two cars?

EMAIL 082: WEEK10M: A car with mass 1700 kg travels at 20 m/s eastward and turns to drive northward at 30 m/s. (a) What is the change of momentum of the car? (b) What is the change of velocity of the car?

EMAIL 083: WEEK10M: A force of 6.00 N acts on a 3.00 kg object for 10.0 s. (a) What is the object's change in momentum? (b) What is its change in velocity?

EMAIL 084: WEEK10T: Laboratory

EMAIL 085: WEEK10F: A glass ball "A" of mass 0.00500 kg moves at a velocity of 0.200 m/s. It collides with a second glass ball "B" of mass 0.0100 kg moving along the same line at a speed of 0.100 m/s. After the collision, ball "A" is still moving with a velocity of 0.080 m/s. (a) What is the original momentum of ball "A"? (b) What is the change in momentum of ball "A"? (c) What is the momentum of Ball "B" after the collision? Ignore effects of friction on the balls.

EMAIL 086: WEEK10F: A car with a mass 1245 kg, moving at 29.0 m/s strikes a 2175 kg car that is at rest. If the two cars stick together in the collision, calculate the joint speed of the cars after the collision. Ignore roadway friction.

EMAIL 087: WEEK10F: A 60 kg dancer leaps 0.32 m upward. (a) What is her momentum just before she makes contact with the grond? (b)What impulse is needed to make her stop? (c) As the dancer lands, the knees bend to give a stopping time of 0.050 seconds. Find the average force exerted on her body?

EMAIL 088: WEEK10F: Figure 9-19 in your book is drawn to scale and it shows the collision of two balls. The ball at the bottom has a mass of 0.600 kg while the ball at the top has a mass of 0.400 kg. Using vector drawing, determine if momentum is conserved in this collision.

EMAIL 071: WEEK09M: How do you answer the question "What keeps a satellite up?"

EMAIL 072: WEEK09M: Two bowling balls each have a mass of 6.8 kg. They are located next to one another with their centers 21.8 cm apart. What gravitational force do they exert on each other.

EMAIL 073: WEEK09M: A satellite is placed in an orbit around the Earth with a radius that is half the radius of the Moon's orbit. Find its period and compare it to the period of the Moon.

EMAIL 074: WEEK09M: Use the data in Table 8-1 to compute the gravitational force that the sun exerts on Jupiter.

EMAIL 075: WEEK09T: Mass Driver Laboratory

EMAIL 076: Week09F: A geosynchronous satellite appears to remain over one spot on Earth. A geosynchronous satellite has an orbital radius of 4.23 x 10⁷ m. (a) Calculate its speed in orbit. (b) Calculate its period.

EMAIL 077: Week09F: The asteroid Ceres has a mass 7 x 10²⁰ kg and a radius of 500 km. (a) What is the acceleration of gravity on its surface? (b) How much would an 85 kg astronaut weigh on Ceres?

EMAIL 078: Week09F: The radius of the earth is about 6.40 x 10³ km. A 7.20 x 10³ N spacecraft travels away from the Earth. What is the weight of the spacecraft at the following distances from the Earth's surface: (a) 6.40 x 10³ km, (b) 1.28 x 10⁴ km

EMAIL 079: Week09F: As an astronaut in an orbiting space shuttle, how would you go about dropping an object down to Earth?

EMAIL 065: WEEK08M: A stone is thrown horizontally at 8.0 m/s from a cliff that is 60.0m high. How far from the base of the cliff will the stone strike the ground? How long does it take to fall?

EMAIL 066: WEEK08M: A dart player throws a dart horizontally at a speed of 12.4 m/s. The dart hits the board 0.32 m below the height from which it was thrown. How far away is the player from the board?

EMAIL 067: WEEK08M: It takes a 615 kg racing car 14.3 s to travel at a uniform speed around a circular racetrack of 50.0 m radius. What is the velocity and acceleration of the car?

EMAIL 068: WEEK08M:A pendulum has a length of 0.67 m. Find its period.

EMAIL 069: WEEK08T: Peridic Motion Laboratory

EMAIL 070: WEEK08F: Test #2, Chapters 3, 4 and 5

EMAIL 056: WEEK07M: Suppose we use a vector of 15 mm to represent a velocity magnitude of 10 m/s. Draw each of the following vectors:

1. 115 m/s north
2. 47 m/s at 40 degrees south of west
3. 75 m/s at 30 degrees east of south

EMAIL 057: WEEK07M: A hiker walks 11 km north, then 21 km at 20 degrees west of north and then 15 km west. At the end of the hike, what is the distance of the hiker from the starting point? What is the hiker's final compass heading (degrees measured to north) as measured from the starting point.

EMAIL 058: WEEK07M: Three forces act simultaneously on a box. One force is 10.0 N north, the second is 15.0 N west, and the third is 15.0 N at 30 degrees east of south. What is the magnitude and direction of the resultant force? What are the north and east components of this resultant force?

EMAIL 059: WEEK07M: Solve for the missing information about athe right triangle:

1. a=20 m, b=65 m, c=?, A=?, B=?, C=?
2. a=80 m, A=20 degrees, c=?, b=?, B=?, C=?
3. c=70 m, B=130 degrees, a=?, b=?, A=?, C=?

EMAIL 060: WEEK07T: Measure the height of a building or tree using triangles. Repeat each measurement 4 times.

1. Build an inclinometer
2. Calibrate it by measuring an object of known height
3. Make measurement on an object of unknown height from three different locations

EMAIL 061: WEEK07F: You place a suitcase weighing 215 N on an inclined plane that makes a 35 degree angle with the horizontal. Draw the gravity force on the suitcase. Draw and measure the two components of this force:

1. The component of the gravity force along the direction of the incline
2. The component of the gravity force perpendicular to the incline.

EMAIL 062: WEEK07F: An object is in equilibrium with three forces acting on it. A 33 N force towards north, a 44 N force at 60 degrees north of east. Make an accurate drawing of the force diagram. What is the magnitude and direction of the third force?

EMAIL 063: WEEK07F: A street lamp weighs 150 N and it is kept in equilibrium by two wires. It is supported equally by two wires that form an angle of 120 degrees with each other. Make an accurate drawing of the force diagram. What is the tension in the wires?

EMAIL 064: WEEK07F: A store wishes to hang a sign weighing 750 N so that cable A attached to the store makes a 30.0 degree angle. Cable B is horizontal and is attached to a neighboring building. Make an accurate drawing of the force diagram. Find the tension in the wires.

EMAIL 051: WEEK06M: Use Newton's laws and discuss each of the following:

1. Why do you have to push harder on the pedals of a bicycle to start it moving than to keep it moving at constant velocity?
2. Suppose you drop a rock from a bridge. Earth pulls down the rock and it accelerates downwards. According to Newton's third law, the rock must also be pulling on earth, yet we don't notice the earth accelerating upward. Why?
3. Why does a package on the seat of a bus slide backward when the bus accelerates quickly from rest? Why does it slide forward when the driver applies the brakes?
4. Suppose the acceleration of an object is zero. Does this mean that there is no force acting on it?
5. When a horse was told to pull a cart, it refused saying that if it pulled the cart forward, according to Newton's Third Law there would be an equal force backwards. According to Newton's Second Law, the cart would not accelerate. True or False?

EMAIL 052: WEEK06M: For each of the following systems, sketch the system and show the forces of action and reaction:

1. A book on a table
2. The 6^th floor in a 20 story building
3. A magnet holding a picture on the refrigerator door
4. A skateboarder rolling down an incline
5. An airplane flying in the air
6. A box sliding on the floor
7. A ball bouncing off the floor
8. The moon in space
9. A car accelerating on a road

EMAIL 053:

WEEK06M: Use Newton's second law and solve for the missing information:

1. m = 50 kg, a = 4.3 m/s² to the east, F = ?
2. F = 2500 N northward, a = 65.5 m/s² northward, m = ?
3. F = 8.30x10¹¹ N to the southwest, m = 7.23 x 10²⁴, a= ?

EMAIL 054: WEEK06T: Complete the lab activity and fill out the reporting form. You will study the kinetic friction force with a block of wood and a spring scale. The scale is used measure the force of friction as you pull blocks with constant velocity. Design and perform experiments that will help you learn about the following:

1. How does the kinetic friction force depend on the surface material? Test three different surfaces (carpet, tabletop, desktop)
2. How does the kinetic friction depend on the normal force? Try adding 50, 100, 150, 200 grams on top of your sliding block.
3. How does the kinetic friction depend on the speed of the block? Measure the friction force while the block travels at 4 different velocities.

EMAIL 055: WEEK06F: No Class!

EMAIL 044: WEEK05M: Test on Chapters 1 and 2

EMAIL 045: WEEK05T: Complete the lab activity and fill out the reporting form.

EMAIL 046: WEEK05F: Discuss each of the following:

1. Why do you have to push harder on the pedals of a bicycle to start it moving than to keep it moving at constant velocity?
2. Suppose you drop a rock from a bridge. Earth pulls down the rock and it accelerates downwards. According to Newton's third law, the rock must also be pulling on earth, yet we don't notice the earth accelerating upward. Why?
3. Why does a package on the seat of a bus slide backward when the bus accelerates quickly from rest? Why does it slide forward when the driver applies the brakes?
4. Why doesn't the moon fall onto the earth?
5. Suppose the acceleration of an object is zero. Does this mean that there is no force acting on it?
6. When a horse was told to pull a cart, it refused saying that if it pulled the cart forward, according to Newton's Third Law there would be an equal force backwards. According to Newton's Second Law, the cart would not accelerate. True or False? Explain.

EMAIL 047: WEEK05F: You place a 7.50 kg television set on a spring scale. If the scale reads 78.4 N, what is the acceleration of gravity at this location?

EMAIL 048: WEEK05F: The maximum force a grocery sack can withstand and not rip is 250 N. If 20 kg of groceries are lifted from the floor to the table with an acceleration of 5 m/s², will the sack hold?

EMAIL 049: WEEK05F: If you use a horizontal force of 30.0 N to slide a 12.0 kg wooden crate across a floor at a constant velocity, what is the coefficient of sliding friction between crate and floor?

EMAIL 050: WEEK05F: A sled of mass 50 kg is pulled along snowcovered, flat ground. The static friction coefficient is 0.30, and the sliding friction coefficient is 0.10.

1. What does the sled weigh?
2. What force will be neded to start the sled moving?
3. What force is needed to keep the sled moving at a constant velocity?
4. Once moving, what total force must be applied to the sled to accelerate it to 3.0 m/s²?

EMAIL 033: WEEK04M: Use the following equations and algebra to solve for the following information:

1. t = 2.00 s, v_I = -2.30 m/s, V_F = 40.0 m/s, a = ____
2. d = 83.0 m, v_I =-10.0 m/s, t = 10.0, v_F = _____
3. v_I = 20.0 m/s, t = 15.0 s, a = 9.00 m/s², d =_____
4. v_F =10.0 m/s, v_I =20.0 m/s, a = -4.00 m/s², d = ____

EMAIL 034: WEEK04M: A ball is thrown upward with a velocity of 30 m/s on top of a 50 m high building. Calculate its velocity and displacement at the times shown in the table. When does the ball reach maximum height? When does it hit the ground?

EMAIL 035: WEEK04M: Measure the time for a ball to roll down an incline for a displacement of 20 cm, 40 cm, 60 cm and 80 cm. Do the data show that the motion has accelerated motion?

EMAIL 036: WEEK04M: The table presents data for the velocity of a object. Graph the data and compute the acceleration of the object during each time interval:

EMAIL 037: WEEK04T: Complete the handout for the acceleration lab.

EMAIL 040: WEEK04F: A car with a velocity of 22 m/s is accelerated uniformly at the rate of 1.6 m/s² for 6.8 s. What is its final velocity? Make a velocity-time graph of this motion.

EMAIL 041: WEEK04F: You are an engineer who must design a runway for airplanes which must have an airspeed velocity of 61 m/s before they can takeoff. The planes are capable of accelerations of 2.5 m/s². Compute the minimum runway length for the following conditions:

1. no wind
2. headwinds of 20 m/s
3. tailwinds of 20 m/s

EMAIL 042: WEEK04F: You have been given the task of building soft barriers on the highway so that cars hitting them will slow down at a safe rate for the passengers. A person wearing a safety belt can withstand a deceleration of 300 m/s². How thick should barriers be to safely stop a car that hits a barrier at 110 km/h?

EMAIL 043: WEEK04F: As a traffic light turns green, a waiting car starts with a constant acceleration of 6.00 m/s². At the instant when the car starts to accelerate, a truck with a constant velocity of 21 m/s passes by in the next lane.

1. Draw velocity-time graphs for the car and truck
2. Draw position-time graphs for the car and the truck.
3. Find out when the car will overtake the truck
4. Find out where the car will overtake the truck
5. Find out how fast the car will be traveling when it overtakes the truck

EMAIL 021: WEEK03M: Figure 3-21 is a position-time graph of two people running.

1. Decribe the positions of runner A relative to runner B at the y-intercepts.
2. Which runner is faster?
3. What is the speed of runner And the speed of runner B?
4. What change hallens at point P?

EMAIL 022: WEEK03M: Look at Figure 3-23a and 3.23b. For each graph, answer the following questions:

1. What kind of motion is represented by the graph? Describe the motion in words.
2. What does the area under the curve of the graph represent?

EMAIL 023: WEEK03M: The total distance a steel ball rollls down an incline is given in the table.

1. Draw a position-time graph of the motion of the ball.
2. Describe the kind of motion that the ball experiences.
3. What distance has the ball rolled by the end of 2.2 s?

EMAIL 024: WEEK03M: The following table lists winning times for races from the 1996 Olympics. Calculate the speed from each competition. What conclusions can be derived from this data?

EMAIL 025: WEEK03H: Assume that you are gathering a crew of 8 people to sail in the Volvo Ocean Race around the world. All the crew members would need to be skilled sailors.

1. Make a list of all the human skills that will be needed on a boat to win the sailboat race.
2. Assuming that each crew member can be an expert in one primary skill area and an "amateur" in one secondary skill area, identify the skills you would seek for each of the crew members.
3. Describe qualities or behaviors of people that would make them bad or poor crew members.
4. How would you screen out people who would not be good crew members?

EMAIL 026: WEEK03H: It has been suggested that the boats should be asked to report on the following observations that the sailors make while traveling:

1. marine life on or near the ocean surface
2. floating human-made refuse or pollution

EMAIL 027: WEEK03H: Construct and test various sailboat designs in a sailboat competition. Record the average speed of each boat and classify boats according to their speed. Each boat should undergo 3 trials. As you design and redesign boats, try out unusual ideas and boat shapes and copy/improve what you think are important design features of the fastest boats.

EMAIL 028: WEEK03H: Drawing Conclusions:

1. Study the designs of the fastest boats for the days competition and discuss what features need to be considered when designing a competition racing boat.
2. Study the designs of the slowest boats for the days competition and discuss what features need to be avoided when designing a competition racing boat.
3. Study all of the boat designs and summarize what ideas still need to be tested.

EMAIL 029: WEEK03F: Light from the sun reaches Earth in 8.3 minutes. The speed of light is 3.00 x 10⁸ m/s. How far is the Earth from the sun? The light coming from the sun was generated deep in its core by hydrogen fusion. The radius of the sun is 6.98 x 10⁶ m and the light takes about 1 million years to reach the surface of the sun. What is the average speed of light flowing from the sun's core to its surface?

EMAIL 030: WEEK03F: You and a friend each drive 50 km from OrangeTown to Greenville. You travel at 90 km/h, your friend at 95 km/h. How long will your friend wait for you at the end of the trip, assuming that you both leave at the same time?

EMAIL 031: WEEK03F: You drive a car 3.0 h at 40 km/h, then 2.0 h at 65 km/h.

1. What is your average velocity if both trips travel eastward?
2. What is your average velocity if the first trip is northward and the second is southward?

EMAIL 032: WEEK03F: Draw the position-time graph for two cars driving to the beach, 50 km from school. Car "A" leaves a store 10 km from school closer to the beach at noon, and drives at 40 km/h. Car "B" starts from school at 12:30PM and drives at 100 km/h. Use the graph to find out when each car arrives at the beach.

EMAIL 011: WEEK02M: Express the following numbers in scientific notation:

• 50000000000
• 0.000000000001842
• 954020000000
• 0.000003470

• 42.3 cm
• 6.2 pm
• 21 km
• 0.023 mm
• 214 microm
• 570 nm

• 248 m
• 64.01 m
• 0.00003 m
• 80.001 m

EMAIL 012: WEEK02M: Make the following computations using the correct significant digits:

• 16.2 m + 5.008 m + 13.48 m
• 13.597 m x 3.65 m
• 2.7 m/0.004326 m
• 5.32 mm +2.1 mm
• 83.3 kg - 12.804 kg

EMAIL 013: WEEK02M: Compute the following values:

• 4.1x10^-10x8.232x10¹⁵/(14.3x10^-9x9.32x10^-25)
• 7.32x10^-6x4.32x10^-20/(2.473x10⁵x6.91x10¹⁰)
• 1543 mm x 5.832 km/ (5.93 Mm x 3.69 pm)
• 6.43 dm x 9.323 nm/ (8.4 m x 143.5 mm)

EMAIL 014: WEEK02H: Use a spherical object and investigate the validity of the laws of Euclidean geometry on the surface of the sphere. Comment on your results.

EMAIL 015: WEEK02H: Measure the circumference (C) and diameter (D) of a circular object. You will have to make up a "protocol" or procedure to get the most accurate and reproducible result for each measurement. The circumference and diameter should be sampled at least 6 times to get an estimate of the standard deviation of your measurements. Compute C/D for each pair of values. Compare the values with the value of PI. and the mean and standard deviation of your circumference and diameter values. Compute the value of C/D from your data.

EMAIL 016: WEEK02H: Compute the mean and standard deviation of your values of PI. What conclusion can you make about the "flatness" of space? What suggestions can you make for followup experiments to study the geometry of space further.

EMAIL 017: WEEK02F: Each cubic centimeter of gold has a mass of 19.3 g. A cube of gold measures 4.23 cm on each edge.

• What is the volume of the cube?
• What is its mass?

EMAIL 018: WEEK02F: Manipulate the equation v = d/t and find the answers to these problems using consistent units:

• Find the distance a bike travels in 1.5 minutes if it is traveling at a constant speed of 20 km/hr.
• How long will it take a car to travel 6000 m if its speed is a constant 30 km/hr?

EMAIL 019: WEEK02F: Water drips from a faucet into a flask at the rate of two drops every three seconds. A cubic centimeter (cm³) contains 20 drops. What volume of water will be collected in one hour?

EMAIL 020: WEEK02F: Tony's Pizza Shop ordered new 23-cm (9-inch) pizza pans. By mistake, 26-cm (10-inch) pans were delivered. Assuming the materials cost for a pizza is 0.25 cents per square centimeter, how much more is a 26-cm diameter pizza worth than a 23-cm diameter pizza. (area of a circle = 2 x PI x Radius²)

EMAIL 001: Define physics in your own words.

EMAIL 002: Why is mathematics important to science? Why is science important to technology?

EMAIL 003: Distinguish among a scientific fact, a hypothesis and a theory.

EMAIL 004: What is the test for whether a hypothesis is scientific or not?

EMAIL 005: Why does science tend to be self-correcting?

EMAIL 006: Theories in science undergo change. Is this a strength or a weakness of science?

EMAIL 007: A meter stick with 1 mm divisions is used to measure a length of 12 cm. What is the absolute error or uncertainty in a measurement with this ruler? What is the relative uncertainty?

EMAIL 008: A stop watch changes in steps of 0.1 seconds. What is the absolute error or uncertainty in a measurement with this stopwatch? What is the minimum time interval that can be measured with a precision of 5%?

EMAIL 009: The following table lists angles that were measured in degrees:

Compute the mean, standard deviation and the standard deviation of the mean for this data.

EMAIL 010: The following table lists volumes that were measured by two different methods, "A" and "B". The values are in milliliters:

Compute the mean, standard deviation and the standard deviation of the mean for each data set (A and B). Decide which data set is more precise.