Unit 3 Progress Check MCQ AP Physics 1

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Transcribed Image Text:AP CallegeBoard AP PHYSICS C: MECHANICS Test Booklet Unit 3 Progress Check: FRQ Read each question carefully. Show all your work for each part of the question. The parts within the question may not have equal weight. 1. o i toq tasitgil od A te In hi C 1. 10 m A ski jumper starts from rest from point A at the top of a hill that is a height h1 above point B at the bottom of the hill. The skier and skis have a combined mass of 80 kg. The skier slides down the hill and then up a ramp and is launched into the air at point C that is a height of 10 m above the ground. The skier reaches point C traveling at 42 m (a) Calculate the height h1. (b) Calculate the speed of the skier as the skier reaches point B. (c) Is the work done by the gravitational force on the ckier o the n point B positive or

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⛔STOP ⛔ Before you look at the answers make sure you gave this practice quiz a try so you can assess your understanding of the concepts covered in Unit 3. Click here for the practice questions: AP Physics 1 Unit 3 Multiple Choice Questions. Facts about the test: The AP Physics 1 exam has 50 multiple choice questions (45 single-select and 5 multiple-select) and you will be given 90 minutes to complete the section. That means it should take you around 15 minutes to complete 8 questions.

The following questions were not written by College Board and, although they cover information outlined in the AP Physics 1 Course and Exam Description, the formatting on the exam may be different. 1. A car is moving around a curve on an interstate highway at 55 mph. What force keeps the car, when turning on the curve, from skidding?

A. Kinetic friction

B. Static friction

C. Normal force

D. Centripetal force

Answer: This one is tricky! Remember that when a tire rolls that the contact point between the tire and road is a "static" contact point. If the friction was kinetic, the tire would be sliding and the car would "skid" and not be able to go through the curve. Also watch out for "centripetal force"...always use the "true" force (friction, normal force, tension, etc.) to represent the inward force.

📄 Study AP Physics 1, Unit 3.1: Vector Fields

2. For the roller coaster pictured, the riders are moving at position "a" and state they feel "lighter" than normal. Which of the following reasons explains why they feel lighter?

A. The riders' seatbelts are loose giving them a feeling of "weightlessness".

B. The riders are getting "pushed out" of their seats and therefore feel lighter at point "a".

C. The normal force for the riders is greater than the weight of the riders, mg.

D. The normal force for the riders is smaller in magnitude than their weight, mg.

Answer: If you draw a free-body diagram for the riders at "a", you would have a shorter arrow pointing up representing the normal force (what they THINK they weigh) and a longer arrow pointing down representing the weight (mg) of the riders. The resulting net force, the centripetal force, would point in toward the center of the circle pictured.

3. For the roller coaster pictured, the riders are moving at position "b" and state they feel "heavier" than normal. Which of the following reasons explains why they feel heavier?

A. The normal force for the riders is greater than the weight of the riders, mg.

B. The normal force for the riders is smaller in magnitude than their weight, mg.

C. The riders are getting "pushed down" in their seats and therefore feel heavier at point "b".

D. The riders' seatbelts are too tight giving them a feeling of "heaviness".

Answer: If you draw a free-body diagram for the riders at "b", you would have a longer arrow pointing up representing the normal force (what they THINK they weigh) and a shorter arrow pointing down representing the weight (mg) of the riders. The resulting net force, the centripetal force, would point in toward the center of the circle pictured.

4. A person is swinging a rock at the end of a string as seen from above. If the string breaks at point "P", at which lettered path will the rock travel?

A. A

B. B

C. C

D. D or E

Answer: As something moves in a circle the string is pulling the object inwards due to the force of tension (the centripetal force). If the object is "let go" as when the string breaks, the object will travel in a straight line tangent to the circle where the force stops acting on the object.

5. A satellite is moving in a circular orbit around the planet Jupiter. Which one feels a greater force?

A. The satellite because Jupiter is so much more massive

B. Jupiter because the satellite has such little mass

C. Jupiter and the satellite feel the exact same force

D. It depends on the distance between the two objects

Answer: Newton's 3rd law--the force between two objects is always equal and opposite. Therefore, Jupiter can only pull on the satellite with the same force that the satellite pulls back on Jupiter.

6. A motorcycle goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the motorcycle due to the road?

A. Inward, perpendicular to the road.

B. Outward, perpendicular to the road.

C. Tangent to the curve in the forward direction.

D. Tangent to the curve opposite the direction of the car's motion.

Answer: In order for the motorcycle to stay on the road, the force of friction (the centripetal force) has to be acting toward the center of the imaginary circle formed by the curve in the road. This means that the friction force must point at a 90 degree angle or perpendicular to the line of motion at that point.

7. A 5.0-kg ball is moving with a constant speed of 2.0 m/s in a horizontal circle whose diameter is 2.0 m. What is the magnitude of the net force on the ball?

A. 0 N

B. 5 N

C. 10 N

D. 20 N

Answer: For this question you'll need to use the equation F = mv^2/r. The tricky part of the math is that you need to recognize the 2.0 m is the diameter and not the radius of the circle. F = (5*2^2)/1 = 20 N of force.

📄 Study AP Physics 1, Unit 3.1: Vector Fields

8. A coin is able to stay on a turntable without sliding. Which of the following is the correct force that keeps the coin from sliding?

A. Centripetal force

B. Weight

C. Normal

D. Friction

Answer: In this case, it is the friction between the coin and the surface of the turntable that keeps the coin from sliding. The normal force is part of the force of friction, however, it is not the only force keeping the coin from sliding. Remember, centripetal force is a term used for the "center-seeking" force but the "true" force is used to explain why the coin stays on the turntable.

9. Two golf balls, 1 and 2, attract each other gravitationally with a force of magnitude F. If we now double both masses but leave the radius the same, what will now be the magnitude of the attractive force on each one?

A. The same force as the original

B. 2 times the original force

C. 4 times the original force

D. Cannot be determined without knowing the acceleration due to gravity

Answer: For this question you should use F = G(m1*m2)/r^2. Since the radius and G don't change, your proportionality is F ~ m1*m2. Since both masses double, Fnew ~ 2m*2m = 4*Foriginal.

📄 Study AP Physics 1, Unit 3.3: Gravitational and Electric Forces

10. A par of tennis balls are held by two students at a distance "D". If the students double the distance, what happens to the force between the tennis balls?

A. 1/4 of the original force

B. 1/2 of the original force

C. 2 of the original force

D. 4 of the original force

Answer: For this question you should use F = G(m1*m2)/r^2. Since the masses and G don't change, your proportionality is F ~ 1/r^2. Since the radius doubles, Fnew ~ 1/2^2 = 1/4*Foriginal.

📄 Study AP Physics 1, Unit 3.3: Gravitational and Electric Forces

11. A student builds a track for a toy car to go around a curve. If the student doubles the radius of the curve, what happens to the acceleration of the car if the speed remains unchanged?

A. The acceleration is 1/4 of the original.

B. The acceleration is 1/2 of the original.

C. The acceleration is 2 times of the original.

D. The acceleration is 4 times of the original.

Answer: Knowing that ac = v^2/r and that the speed stays the same, the proportionality is ac ~ 1/r. If the radius is doubled, then ac(new) = 1/2 ac(original).

12. A student places a rock in a sling and whirls it around her head. If the student then places an additional, equal mass rock in the sling and keep the radius the same, how much more force will she need in order to keep the rocks moving at the same tangential velocity?

A. 1/4 of the original

B. 1/2 of the original

C. 2 times the original

D. 4 times the original

Answer: Using the equation Fc = mv^2/r, if you double the mass and keep the speed and the radius the same, then the proportionality becomes Fc ~ m. Doubling the mass then makes the proportionality Fc(new) = 2*Fc(original).

📄 Study AP Physics 1, Unit 3.1 Vector Fields

13. A student is riding a roller coaster and finds himself upside-down at the top of a loop. Which force keeps him in the seat of the roller coaster car?

A. Weight

B. Force due to gravity

C. Tension

D. Normal Force

Answer: At the top of the circle, both mg and the normal force act on the person. The normal force keeps the person in the seat since it is the contact force between the rider and the car.

📄 Study AP Physics 1, Unit 3.1: Vector Fields

14. For an object moving in a circle at a constant speed, which of the following constantly changes?

A. Velocity

B. Speed

C. Mass

D. Radius

Answer: Remember that velocity is a vector and changes as the direction changes! Speed, mass, and radius will not change for a particular circle.

15. If a person feels "weightless" at the top of a roller coaster hill, which of the following forces would be "missing" from the free-body diagram?

A. Tension

B. Normal Force

C. Weight (mg)

D. Friction

Answer: Your "apparent weight", or the weight you "feel", is really your normal force, not your "actual weight". Your "actual weight" is determined by your mass and the acceleration due to gravity (mg).

📄 Study AP Physics 1, Unit 3.1: Vector Fields

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