Question

An object is placed on the moveable piston of a cylinder filled with a gas. The object exerts a downward force F on the piston that accelerates the piston downward, compressing the gas. Which of the following is a correct description of the magnitude of the upward force exerted by the piston on the object?

a. The force exerted by the piston on the object is equal to FF.
b. The force exerted by the piston on the object is less than FF because the piston is accelerating downward.
c. The force exerted by the piston on the object is greater than F because the gas exerts an upward force on the piston.
d. The force exerted by the piston cannot be compared to FF without knowing the magnitude of the acceleration of the piston and pressure of the gas.

Answer 1

Answer:

b. The force exerted by the piston on the object is less than F because the piston is accelerating downward.

Explanation:

Given that object exerts a downward force F on the piston that accelerates the piston downward.

An object can accelerate if the net force acting on it is non-zero.

Here, the piston is acceleration in the downward direction, so the net for on the piston is in the downward direction.

Force due to object, F, is in the downward direction while the force exerted by the piston on the object is in the upward direction.

As the acceleration of the piston is in the downward direction, so the downward force is more.

Therefore, the force exerted by the piston on the object is less than F because the piston is accelerating downward.

Hence, option (b) is correct.