AP Physic 1: Unit 2: MCQ Part A

An object is at rest on the ground. The object experiences a downward gravitational force from Earth. Which of the following predictions is correct about why the object does not accelerate downward? Select two answers. Justify your selections.

-The bonded molecules of the object are repelled upward by the bonded molecules of the ground with the same magnitude as the gravitational force downward on the object. -The normal force is exerted upward on the object from the ground with the same magnitude as the gravitational force downward on the object.

A satellite orbits Earth. The only force on the satellite is the gravitational force exerted by Earth. How does the satellite's acceleration compare to the gravitational field at the location of the satellite? Select two answers.

-The gravitational field and the acceleration point in the same direction. -The magnitudes of the acceleration and the gravitational field strength are equal.

A student sets up an experiment to determine the inertial mass of a cart. The student has access to the following measurement equipment: a spring scale, a meterstick, and a stopwatch. The student uses the spring scale to pull the cart starting from rest along a horizontal surface such that the reading on the spring scale is always constant. All frictional forces are negligible. In addition to the spring-scale reading, which two of the following quantities could the student measure with the available equipment and then use to determine the inertial mass of the cart? Select two answers.

-The total distance traveled by the cart after it has been in motion -The time during which the cart is in motion

If the mass of block BB is 2kg2kg, the gravitational force exerted on block BB is most nearly which of the following?

20N

A 5kg5⁢kg object is released from rest near the surface of a planet such that its gravitational field is considered to be constant. The mass of the planet is unknown. After 2s2⁢s, the object has fallen 30m30m. Air resistance is considered to be negligible. What is the gravitational force exerted on the 5kg5⁢kg object near the planet's surface?

75N

At time t=0s, object X of mass M travels at a constant speed of 2 m/s to the right toward object Y of mass 2M that is a distance of 8m away from object X while at rest, as shown above. Both objects are on a horizontal surface, where the frictional forces may be considered negligible. Which of the following pairs of force diagrams represents the forces exerted on object X and object Y at t=4 s?

B graph

The two blocks eventually stop and reverse direction. Which of the following graphs best predicts the acceleration of block AA as it moves up and down the rough, inclined surface? Assume that the positive direction points down the slope.

B) ---- ---- ------------->

A toy car has a battery-powered fan attached to it such that the fan creates a constant force that is exerted on the car so that it is propelled in the opposite direction in which the fan blows air. The car has a carriage that allows a student to attach objects of different masses, as shown above. The fan has only one speed setting. All frictional forces are considered to be negligible. Which of the following procedures could be used to determine how the mass of the fan-car-object system affects the acceleration of the system?

Measure the mass of the system using a balance, activate the fan, measure the distance traveled by the system at a known time by using a stopwatch, and repeat the experiment for several trials with different objects added to the carriage.

A block of mass M is attached to a modified Atwood machine and is accelerated upward at 3a by a constant force F0. What is the weight of the block?

Mg

A block is placed on an inclined plane and remains stationary, as shown in the figure above. A student claims, "The block remains stationary because as gravity tries to pull the block down the ramp, the block exerts an equal and opposite force on itself up the ramp." Is the student's claim correct? Justify your answer.

No. Newton's third law states the block cannot exert a force on itself.

Identical spheres are dropped from a height of 100m above the surfaces of both Planet X and Planet Y. The position of the spheres as a function of time is recorded as the spheres fall. These data are shown in the graphs above. Which planet exerts a greater gravitational force on the sphere, and what evidence supports this conclusion?

Planet Y, because the magnitude of the slope of the curve increases at a faster rate.

A 1500kg car traveling along a road is hit by a 0.1kg rock that creates a small crack in the car's windshield. Which of the following describes the interaction between the windshield and the rock?

The car exerts a force on the rock, and the rock exerts a force on the car. The two forces are equal in magnitude.

Two students, Student X and Student Y, stand on a long skateboard that is at rest on a flat, horizontal surface, as shown. In order to get the student-student-skateboard system to accelerate, Student X claims that Student Y should apply a force on Student X while both students stand on the skateboard. Which of the following statements is true regarding the claim made by Student X?

The claim is incorrect because both students are internal to the student-student-skateboard system, and internal forces within a system cannot cause the system to accelerate.

Two objects, X and Y, move toward one another and eventually collide. Object X has a mass of 2M and is moving at a speed of 2v0 to the right before the collision. Object Y has a mass of M and is moving at a speed of v0 to the left before the collision. Which of the following describes the magnitude of the forces F the objects exert on each other when they collide?

The force exerted by X on Y is F to the right, and the force exerted by Y on X is F to the left.

A student pulls a block over a rough surface with a constant force Fp that is at an angle θ above the horizontal, as shown above. If Fp remains constant but the angle θ is increased, which of the following is true at some later time?

The force of friction between the block and surface will decrease.

Students connect a spring scale to a block on a rough horizontal surface. The students use the spring scale to measure the magnitude of the horizontal force needed to pull the block at a constant speed. Which of the following statements explains why two forces exerted between objects are equal in magnitude?

The frictional forces that the block and the surface exert on each other, because objects always exert forces of equal magnitude on each other.

A spring-loaded launcher has a mass of 0.60 kg and is placed on a platform 1.2m above the ground. The force of friction is negligible between the platform and the launcher. The launcher fires a 0.30kg ball that lands a distance D to the right of the platform, as shown in the diagram above. Which of the following explanations is true?

The launcher will fall off the platform and land D/2 to the left of the platform because the launcher is twice the mass of the ball.

A student uses an electronic force sensor to study how much force the student's finger can apply to a specific location. The student uses one finger to apply a force on the sensor, and data collected from two trials are shown in the table. During which trial, if any, does the student's finger experience the greatest electromagnetic force?

Trial 2, because the student's finger applied the largest force to the sensor.

Which of the following experiments could be used to determine the inertial mass of a block?

Use a spring scale to exert a force on the block. Measure the acceleration of the block and the applied force.

The amusement park ride shown above takes riders straight up a tall tower and then releases an apparatus holding seats. This apparatus free-falls back to Earth and is stopped safely right above the ground. Which of the following indicates the magnitude of the gravitational force exerted on a rider of mass mm on the way up and on the way down?

Way Up: Equal to Mg Way Down: Equal to Mg

Two identical blocks, block A and block B, are placed on different horizontal surfaces. Block A is initially at rest on a smooth surface, while block B is initially at rest on a rough surface. A constant horizontal force of magnitude F0 is exerted on each block. After the force has been applied for a time Δt, the speeds of blocks A and B are vA and vB, respectively. Which of the following claims indicates the correct relation between vA and vB and provides the best justification for the relation?

vA>vB. The forces between the atoms in a block and the atoms in a surface oppose the motion of the block and are greater, on average, for block B.