Simple F=ma Practice

Two objects, A and B, move toward one another. Object A has twice the mass and half the speed of object B. Which of the following describes the forces the objects exert on each other when they collide and provides the best explanation?

• The force exerted by A on B will be twice as great as the force exerted by B on A, because A has twice the mass of B.

• The force exerted by A on B will be half as great as the force exerted by B on A, because A has half the speed of B.

• The forces exerted by A on B will be twice as great as the force exerted by B on A, because A has half the speed of B.

• The forces exerted by each object on the other are the same, because interacting objects cannot exert forces of different magnitude on each other.

For which of the following objects will be the net force acting on it be zero?

• A football is thrown straight up into the air.

• A hamburger in free-fall.

• A crate being pushed uphill at constant speed.

• A mine cart traveling uphill and slowing down until it rolls back down the hill.

Which of the following expressions cannot be used to represent the acceleration of the spooky system shown?

• $\frac{F_3}{6m}$

• $\frac{F_2}{2m}$

• $\frac{F_1}{3m}$
  

• All of the above could be used to represent the acceleration of the system

A student with a mass of 50 kg is standing on a bathroom scale while riding an elevator. No one is quite sure what the student is trying to accomplish, but the reading on the scale is 400 N. Which of the following is a correct description of the elevator’s motion?

• Moving upward with increasing speed

• Moving downward with constant speed

• Moving downward with decreasing speed

• Moving downward with increasing speed

Block A goes the down an incline with decreasing angle of inclination as shown. Which of the following is true?

• The acceleration of the block increases as it slides down.

• The acceleration of the block decreases as it slides down.

• The acceleration of the block stays the same as it slides down the incline.

• ( ͡° ͜ʖ ͡°)

A skier slides down an incline that makes an angle of 30^o with the horizontal. At the bottom of the incline, the skier continues on a horizontal surface. All surfaces are frictionless. Which of the following graphs could show the position of the skier as a function of time? (dashed line represents leaving the incline).

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• 
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A teacher drags a suitcase across the ground at Miami International Airport after running away from teaching virtually. The frictional force of the floor on a large suitcase is least when the suitcase is:

• dragged by a force parallel to the floor

• pulled by a force directed at an angle above the floor.

• pushed by a force directed at an angle into the floor

• turned on its side and pushed by a force parallel to the floor.

A box at rest on a horizontal surface is weighing 20N.The coefficient of static friction between the box and the surface is 0.50. What static frictional force is needed to move the box?

• 10 m/s²

• 0.5 m/s²

• 1.0 m/s²

• 4.0 m/s²