A ball of mass 0.7 kg strikes the wall at an angle of 90 degrees with speed 72 km/h. Consider that the bounce lasts for 0.1 s and is perfectly elastic. What is the magnitude of the average reaction force from the wall that acts on the ball?
initial speed: v = 72 km/h = 20 m/s.
mass: m = 0.7 kg
time of the impact: t = 0.1 s
average force: F
The speed after impact is the same as initial speed, but velocity has got the opposite direction. Therefore, Δv = 2v
Δmomentum = Δp = mΔv = 2mv
from the Newton's 2nd Law:
F = Δp/Δt = 2mv/t
F = 20.720/(0.1) = 280 N
Answer: The magnitue of the average force equals 280 N.
FM
Related Physics A Level answers
All answers ▸Explain how bright fringes arise in Young's double slit experiment
A DVD is dropped from rest. The DVD does not reach terminal velocity before it hits the ground. Explain how the acceleration of the DVD varies from the instant it is dropped until just before it hits the ground.
Describe and explain the photoelectric effect (6 marks)
A car of mass 1500kg is travelling at 10 ms-1 along a horizontal road. A brake force of 3000N brings it to rest. Calculate the deceleration of the car and the distance travelled by the car whilst decelerating.