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## Homework Statement

A mass m is fired straight up from a cannon, through the air, it rises to a maximum height, and then it falls back down to its initial height. There is air resistance. Consider these three statement.

I. The work done by the force of gravity during the flight is Zero.

II. The work done by the force of friction during the flight is zero.

How many of these statements are true?

A.) All are true./

B.) None are true.

C.) Only statement I is true

D) Only statement II is true.

Only statement II is true.

## Homework Equations

when a mass is brought to rest, the work done by the frictional force on it is equal to the kinetic energy of the object, KE=1/2 mv2. (friction) Newton’s universal law of gravitation:

F = Gm1m2/r2,

where F is the force due to gravity, between two masses (m1 and m2), which are a distance r apart; G is the gravitational constant.

## The Attempt at a Solution

At first I thought statement C was true, but because When an object is falling freely, the force of gravity is doing work against the resistance from inertia and the air resistance or drag on the object. So I am thinking both statements are false because gravity is doing work against the resistance from inertia and the air resistance or drag on the object. The forces acting on the object are gravity and the opposite or resistive forces of inertia and air resistance.

Because the question is saying that both gravity and air friction arent doing any work when the object falls

i think none are true

and isnt air resistance kinetic energy? Thanks for your help! :)

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