Question

A ball is dropped from a height of 20 m.
Calculate the average acceleration of the
ball.
b. Calculate the average velocity for
its downward motion until it hits the
ground.
c. Find the time taken for the ball to hit the
ground.
11​

Answer 1

Answer:

Velocity just before the collision will be V

1

=

2gh

1

=

2×10×20

=20m/s (downward)

the rebound velocity will be V

2

=−

2gh

2

=−

2×10×5

=−10m/s negative because upward i.e opposite

to initial velocity.

Now change in momentum will be ΔP=m(V

2

−V

1

)=m(−10−20)=−30m

so average force will be F=

Δt

ΔP

=

0.01

−30m

=−3000m

so average acceleration will be a=

m

F

=−3000m/s

2

negative because it was opposite to initial direction of motion.