AP Physics I Final Exam Review

41 You are standing on a straight stretch of road and watching the motion of a bicycle; you choose your position as the origin. At one instant, the position of the bicycle is negative and its velocity is positive. Is the bicycle getting closer to you or farther away? Explain.

If the position of the bicycle is negative it is to your left. The bicycle's velocity is positive, or to the right, so the bicycle is getting closer to you.

145 If you are standing still, the upward normal force on you from the floor is equal in magnitude to the weight force that acts on you. But it's possible to move so that the normal force is greater than your weight. Explain how this could be done.

If you jump up, during the initial phase when you are still in contact with the floor, you are accelerating upward. This means the net force on you must be upward, so the upward normal force must be bigger than the downward weight force.

47B For each motion diagram shown in the figure, determine the sign (positive or negative) of the acceleration. (Figure 1) Diagram (b).

Negative

47C For each motion diagram shown in the figure, determine the sign (positive or negative) of the acceleration. (Figure 1) Diagram (c).

Negative

45B Determine the sign (positive or negative) of the position and the velocity for the motion diagram in (Figure 2)?

Negative position, negative velocity

45A Determine the sign (positive or negative) of the position and the velocity for the motion diagram in (Figure 1)?

Negative position, positive velocity

130 Alyssa pushes to the right on a filing cabinet; the friction force from the floor pushes on it to the left. Because the cabinet doesn't move, these forces have the same magnitude. Do they form an action/reaction pair?

No

15A Shannon decides to check the accuracy of her speedometer. She adjusts her speed to read exactly 70 mph on her speedometer and holds this steady, measuring the time between successive mile markers separated by exactly 1.00 mile. If she measures a time of 47 s, is her speedometer accurate?

No

135B A spring-loaded gun shoots a plastic ball. The trigger has just been pulled and the ball is starting to move down the barrel. The barrel is horizontal. Identify all the forces acting on the ball.

Normal, spring, weight, kinetic friction

137A If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Identify all of the forces acting on you as the car travels in a straight line at a perfectly steady speed on level ground.

Normal, weight

137C If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Identify all of the forces acting on you as the car slowing down.

Normal, weight

136B A bag of groceries is on the back seat of your car as you stop for a stop light. The bag does not slide. Identify all the forces acting on the

Normal, weight, static friction

142B A sprinter has just started a race and is speeding up as she runs down the track. The sprinter is running to the right. Identify all the forces acting on the sprinter.

Normal, weight, static friction

47A For each motion diagram shown in the figure, determine the sign (positive or negative) of the acceleration. (Figure 1) Diagram (a).

Positive

45C Determine the sign (positive or negative) of the position and the velocity for the motion diagram in (Figure 3)?

Positive position, negative velocity

10B A garden has a circular path of radius 50 m. John starts at the easternmost point on this path, then walks counterclockwise around the path until he is at its southernmost point. What is the direction of John's displacement?

Southwest

139 Josh and Taylor, standing face-to-face on frictionless ice, push off each other, causing each to slide backward. Josh is much bigger than Taylor. After the push, which of the two is moving faster?

Taylor will be moving faster.

4 A car travels along a straight east-west road. A coordinate system is established on the road, with x increasing to the east. The car ends up 16 mi west of the origin, which is defined as the intersection with Mulberry Road. If the car's displacement was -27 mi , what side of Mulberry Road did the car start on? How far from the intersection was the car at the start?

The car started 11 mi east of Mulberry Road.

137F If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Use Newton's laws to explain why you seem to be "thrown forward" as the car stops. Is there really a force pushing you forward?

The net force on you has remained zero because the net vertical force is zero and there are no horizontal forces. According to Newton's first law, if the net force on you is zero, then you continue to move in a straight line with a constant velocity. That is what happens to you when the car slows down. You continue to move forward with a constant velocity.

138 A beach ball is thrown straight up, and some time later it lands on the sand. Is the magnitude of the net force on the ball greatest when it is going up or when it is on the way down? Or is it the same in both cases? Explain. Air resistance should not be neglected for a large, light object.

The only contact force is the force of air drag on the ball. The only long-range force is the weight of the ball. Drag always points in the direction opposite to the motion. Thus the weight of the ball and the drag force always reinforce each other if the ball is moving straight up. The net force is larger on the way up.

147 (ADD IMAGE) The tire on this drag racer is severely twisted: The force of the road on the tire is quite large (most likely several times the weight of the car) and is directed forward as shown in (Figure 1) Is the car speeding up or slowing down? Explain

The way the tire is twisted indicates that the force of the road on the tire is forward. Since this force is likely greater than the backward air resistance force, the net force is also forward; therefore, the car is accelerating in the forward direction.

50A A student at the top of a building of height h throws ball A straight upward with speed v0 and throws ball B straight downward with the same initial speed. Compare the ball's accelerations, both direction and magnitude, immediately after they leave her hand. Is one acceleration larger than the other? Or are the magnitudes equal?

They are equal

50B A student at the top of a building of height h throws ball A straight upward with speed v0 and throws ball B straight downward with the same initial speed. Compare the final speeds of the balls as they reach the ground.

They are equal

15B Shannon decides to check the accuracy of her speedometer. She adjusts her speed to read exactly 70 mph on her speedometer and holds this steady, measuring the time between successive mile markers separated by exactly 1.00 mile. If not, is the speed it shows too high or too low?

Too low

144B You've slammed on the brakes and your car is skidding to a stop while going down a 20º hill. Identify all the forces acting on the car

Weight, kinetic friction, normal

143B A basketball player is getting ready to jump, pushing off the ground and accelerating upward. Identify all the forces acting on the basketball player.

Weight, normal

131 (ADD IMAGE) Figure 1 shows a situation in which the force of the road on the car's tire points forward. In other situations, the force points backward. Give an example of such a situation.

When the car is going forward and slowing down.

137E If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Describe what happens to you as the car slows down.

You continue to move forward with the initial speed of the car.

49C We set the origin of a coordinate system so that the position of a train is x = 0 m at t = 0 s. (Figure 1) shows the train's velocity graph. Find the acceleration of the train at t=3.0s

a=1.0m/s^2

42 Give an example of a trip you might take in your car for which the distance traveled as measured on your car's odometer is not equal to the displacement between your initial and final positions.

circular motion with a constant speed

149 Scallops use jet propulsion to move from one place to another. Their shells make them denser than water, so they normally rest on the ocean floor. If a scallop wishes to remain stationary, hovering a fixed distance above the ocean floor, it must eject water _____ so that the thrust force on the scallop is _____.

downward, upward

43 A car travels to the left at a steady speed for a few seconds, then brakes for a stop sign. Select the correct motion diagram of the car for the entire motion described here. The dots are numbered in order, starting with zero.

image

44 A softball player slides into second base. Use the particle model to draw a motion diagram of the player from the time he begins to slide until he reaches the base. Number the dots in order, starting with zero.

image

48 (Figure 1) shows the velocity graph of a bicycle. Choose the correct bicycle's acceleration graph for the interval 0s≤t≤4s

image

49A We set the origin of a coordinate system so that the position of a train is x = 0 m at t = 0 s. (Figure 1) shows the train's velocity graph. Choose the correct position graph for the train.

image

49B We set the origin of a coordinate system so that the position of a train is x = 0 m at t = 0 s. (Figure 1) shows the train's velocity graph. Choose the correct acceleration graph for the train.

image

134 A person is pushing horizontally on a box with a constant force, causing it to slide across the floor with a constant speed. If the person suddenly stops pushing on the box, the box will

immediately begin slowing down and eventually stop.

148 A group of students is making model cars that will be propelled by model rocket engines. These engines provide a nearly constant thrust force. The cars are light-most of the weight comes from the rocket engine-and friction and drag are very small. As the engine fires, it uses fuel, so it is much lighter at the end of the run than at the start. A student ignites the engine in a car, and the car accelerates. As the fuel burns and the car continues to speed up, the magnitude of the acceleration will

increase

1B One consequence of Einstein's theory of special relativity is that mass is a form of energy. This mass-energy relationship is perhaps the most famous of all physics equations: E = mc^2 where m is mass, c is the speed of the light, and E is the energy. In SI units, the units of speed are m/s. For the preceding equation to have consistent units (the same units on both sides of the equation), the units of E must be what

(kg*m^2)/s^2

146B Normally, jet engines push air out the back of the engine, resulting in forward thrust, but commercial aircraft often have thrust reversers that can change the direction of the ejected air, sending it forward. When might these thrust reversers be useful in practice?

-If the ejected air is directed downward, the thrust force is up. Jets can take off vertically without needing a runway this way. -If the ejected air is directed forward then thrust force is backward. This might be desirable to slow the plane down.

13D The bacterium Escherichia coli (or E. coli) is a single-celled organism that lives in the gut of healthy humans and animals. Its body shape can be modeled as a 2-μm-long cylinder with a 1 μm diameter, and it has a mass of 1×10^−12 g. Its chromosome consists of a single double-stranded chain of DNA 700 times longer than its body length. The bacterium moves at a constant speed of 20 μm/s though not always in the same direction. Answer the following questions about E. coli using SI units (unless specifically requested otherwise) and correct significant figures. (Figure 1) What is the length of its DNA, in millimeters?

1 mm

29 Weddell seals make holes in sea ice so that they can swim down to forage on the ocean floor below. Measurements for one seal showed that it dived straight down from such an opening, reaching a depth of 0.30 km in a time of 5.0 min. What was the speed of the diving seal?

1.0 m/s

25 A rectangle has length 3.24 m and height 0.432 m. To the correct number of significant figures, what is its area?

1.40 m^2

24 The earth formed 4.57×10^9 years ago. What is this time in seconds?

1.44E+17s

8 Estimate the average speed, in m/s, with which the hair on your head grows. Make this estimate from your own experience noting, for instance, how often you cut your hair and how much you trim.

10E-8m/s

27 A person walks briskly at 2.10 m/s. How much time will it take them to walk one mile?

12.8 min

13C The bacterium Escherichia coli (or E. coli) is a single-celled organism that lives in the gut of healthy humans and animals. Its body shape can be modeled as a 2-μm-long cylinder with a 1 μm diameter, and it has a mass of 1×10^−12 g. Its chromosome consists of a single double-stranded chain of DNA 700 times longer than its body length. The bacterium moves at a constant speed of 20 μm/s though not always in the same direction. Answer the following questions about E. coli using SI units (unless specifically requested otherwise) and correct significant figures. (Figure 1) What is its mass?

1E-15 kg

13B The bacterium Escherichia coli (or E. coli) is a single-celled organism that lives in the gut of healthy humans and animals. Its body shape can be modeled as a 2-μm-long cylinder with a 1 μm diameter, and it has a mass of 1×10^−12 g. Its chromosome consists of a single double-stranded chain of DNA 700 times longer than its body length. The bacterium moves at a constant speed of 20 μm/s though not always in the same direction. Answer the following questions about E. coli using SI units (unless specifically requested otherwise) and correct significant figures. (Figure 1) What is its diameter?

1E-6 m

13E The bacterium Escherichia coli (or E. coli) is a single-celled organism that lives in the gut of healthy humans and animals. Its body shape can be modeled as a 2-μm-long cylinder with a 1 μm diameter, and it has a mass of 1×10^−12 g. Its chromosome consists of a single double-stranded chain of DNA 700 times longer than its body length. The bacterium moves at a constant speed of 20 μm/s though not always in the same direction. Answer the following questions about E. coli using SI units (unless specifically requested otherwise) and correct significant figures. (Figure 1) If the organism were to move along a straight path, how many meters would it travel in one day?

2 m

34 A student walks 1.6 mi west and then 1.6 mi north. Afterward, how far is she from her starting point?

2.3 mi

140 A 6.0 kg block has an acceleration of 0.40 m/s^2 when a force is exerted on it. A second block has an acceleration of 0.10 m/s^2 when subject to the same force. What is the mass of the second block?

24kg

28 A bird flies 3.6 km due west and then 2.1 km due north. Another bird flies 2.1 km due west and 3.6 km due north. What is the angle between the net displacement vectors for the two birds?

29 degrees

13A The bacterium Escherichia coli (or E. coli) is a single-celled organism that lives in the gut of healthy humans and animals. Its body shape can be modeled as a 2-μm-long cylinder with a 1 μm diameter, and it has a mass of 1×10−^12 g. Its chromosome consists of a single double-stranded chain of DNA 700 times longer than its body length. The bacterium moves at a constant speed of 20 μm/s though not always in the same direction. Answer the following questions about E. coli using SI units (unless specifically requested otherwise) and correct significant figures. (Figure 1) What is its length?

2E-6 m

26 Compute 3.24 m + 0.432 m to the correct number of significant figures.

3.67 m

30 A bird flies 3.8 km due west and then 2.4 km due north. What is the magnitude of the bird's displacement?

4.5 km

14 Motor neurons in mammals transmit signals from the brain to skeletal muscles at approximately 25 m/s. Estimate how much time in ms (10^−3s) it will take for a signal to get from your brain to your hand.

40 ms

9 Blades of grass grow from the bottom, so, as growth occurs, the top of the blade moves upward. During the summer, when your lawn is growing quickly, estimate this speed, in m/sm/s. Make this estimate from your experience noting, for instance, how often you mow the lawn and what length you trim.

4×10E-8m/s

23 An object's average density ρ is defined as the ratio of its mass to its volume: ρ=M/V. The earth's mass is 5.94×10^24kg, and its volume is 1.08×10^12km^3. What is the earth's average density?

5.50×10^3kg/m^3

11C The images of trees in the figure come from a catalog advertising fast-growing trees. If we mark the position of the top of the tree in the successive years, as shown in the graph in the figure, we obtain a motion diagram much like ones we have seen for other kinds of motion. The motion isn't steady, of course. In some months the tree grows rapidly; in other months, quite slowly. We can see, though, that the average speed of growth is fairly constant for the first few years. (Figure 1) At the end of year 3, a rope is tied to the very top of the tree to steady it. This rope is staked into the ground 15 feet away from the tree. What angle does the rope make with the ground?

63 degrees

10A A garden has a circular path of radius 50 m . John starts at the easternmost point on this path, then walks counterclockwise around the path until he is at its southernmost point. What is the magnitude of John's displacement?

71m

11A The images of trees in the figure come from a catalog advertising fast-growing trees. If we mark the position of the top of the tree in the successive years, as shown in the graph in the figure, we obtain a motion diagram much like ones we have seen for other kinds of motion. The motion isn't steady, of course. In some months the tree grows rapidly; in other months, quite slowly. We can see, though, that the average speed of growth is fairly constant for the first few years. (Figure 1) What is the tree's speed of growth, in feet per year, from t=1yr to t=3yr?

9 ft/yr

11B The images of trees in the figure come from a catalog advertising fast-growing trees. If we mark the position of the top of the tree in the successive years, as shown in the graph in the figure, we obtain a motion diagram much like ones we have seen for other kinds of motion. The motion isn't steady, of course. In some months the tree grows rapidly; in other months, quite slowly. We can see, though, that the average speed of growth is fairly constant for the first few years. (Figure 1) What is the tree's speed in m/s?

9E10-8 m/s

31 Which of the following motions is described by the motion diagram of the figure? (Figure 1)

A car pulling away from a stop sign

32 Which of the following motions could be described by the motion diagram of the (Figure 1) ?

A cyclist braking to a stop.

12A The bacterium Escherichia coli (or E. coli), is a single-celled organism that lives in the gut of healthy humans and animals. When grown in a uniform medium rich in salts and amino acids, it swims along zig-zag paths at a constant speed. (Figure 1) shows the positions of an E. coli as it moves from point A to point J. Each segment of the motion can be identified by two letters, such as segment BC. During which segments, if any, does the bacterium have the same displacement?

AB and CD

12C The bacterium Escherichia coli (or E. coli), is a single-celled organism that lives in the gut of healthy humans and animals. When grown in a uniform medium rich in salts and amino acids, it swims along zig-zag paths at a constant speed. (Figure 1) shows the positions of an E. coli as it moves from point A to point J. Each segment of the motion can be identified by two letters, such as segment BC. During which segments, if any, does the bacterium have the same velocity?

AB and CD

135A A spring-loaded gun shoots a plastic ball. The trigger has just been pulled and the ball is starting to move down the barrel. The barrel is horizontal. Select a correct motion diagram.

ADD IMAGE

136A A bag of groceries is on the back seat of your car as you stop for a stop light. The bag does not slide. Select a correct motion diagram for the bag.

ADD IMAGE

137B If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Draw your free-body diagram. Suggest that the car is moving to the right.

ADD IMAGE

137D If a car stops suddenly, you feel "thrown forward." We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold on to. Draw your free-body diagram if the car slowing down. Suggest that the car is moving to the right.

ADD IMAGE

142A A sprinter has just started a race and is speeding up as she runs down the track. The sprinter is running to the right. Draw a motion diagram.

ADD IMAGE

143A A basketball player is getting ready to jump, pushing off the ground and accelerating upward. Select a correct motion diagram.

ADD IMAGE

144A You've slammed on the brakes and your car is skidding to a stop while going down a 20º hill. Select a correct motion diagram for this situation.

ADD IMAGE

12B The bacterium Escherichia coli (or E. coli), is a single-celled organism that lives in the gut of healthy humans and animals. When grown in a uniform medium rich in salts and amino acids, it swims along zig-zag paths at a constant speed. (Figure 1) shows the positions of an E. coli as it moves from point A to point J. Each segment of the motion can be identified by two letters, such as segment BC. During which segments, if any, does the bacterium have the same speed?

All paths

133 Suppose you are an astronaut in deep space, far from any source of gravity. You have two objects that look identical, but one has a large mass and the other a small mass. How can you tell the difference between the two?

Assuming you can exert a reproducible force in throwing both objects, you could throw each and note the acceleration each obtains.

141 Dave pushes his four-year-old son Thomas across the snow on a sled. As Dave pushes, Thomas speeds up. Which statement is true?

Both forces have the same magnitude.

132 (ADD IMAGE) Three arrows are shot horizontally. They have left the bow and are traveling parallel to the ground as shown in the figure. Air resistance is negligible. Rank in order, from largest to smallest, the magnitudes of the horizontal forces F1, F2, and F3 acting on the arrows. Some may be equal. State your reasoning.

F1=F2=F3=0 because there is no change in the horizontal motion of the arrows.

146A Normally, jet engines push air out the back of the engine, resulting in forward thrust, but commercial aircraft often have thrust reversers that can change the direction of the ejected air, sending it forward. How does this affect the direction of thrust?

If the ejected air is directed forward then thrust force is backward (Newton's 3rd law).

1A Gravity causes objects to be attracted to one another. This attraction keeps our feet firmly planted on the ground and causes the moon to orbit the earth. The force of gravitational attraction is represented by the equation F = (Gm1m2)/r^2 where F is the magnitude of the gravitational attraction on either body, m1 and m2 are the masses of the bodies, r is the distance between them, and G is the gravitational constant. In SI units, the units of force are kg⋅m/s^2, the units of mass are kg, and the units of distance are m. For this equation to have consistent units, the units of G must be what?

m^3/kg*s^2

33 You throw a rock upward. The rock is moving upward, but it is slowing down. If we define the ground as the origin, the position of the rock is _____ and the velocity of the rock is _____.

positive, positive

46 A Thompson's gazelle can reach a speed of 13 m/s in 3.0 s . A lion can reach a speed of 9.5 m/s in 1.0 s . A trout can reach a speed of 2.8 m/s in 0.12 s . Which animal has the greatest acceleration

trout