Aboy throws a ball of mass 0.25 kg straight upward with an initial speed of 20 m/s. when the ball returns to the boy, its speed is 17 m/s. how much work does air resistance do on the ball during its flight?

The work done is 13.875 J.

Explanation:

Given that,

Mass of ball = 0.25 kg

Initial speed = 20 m/s

Final speed = 17 m/s

We need to calculate the work done

Using formula of work done

Work done by the friction

Negative sign shows the friction always against displacement.

Hence, The work done is 13.875 J.

the answer is to check all of them! they all apply well at least i think so!

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.