A force of 100N was used to kick a football of mass 0.8kg. Find the velocity with which the ball moves if it takes 0.8s to be kicked
A
\(32ms^{-1} \)
B
\(50ms^{-1} \)
C
\(64ms^{-1} \)
D
\(100ms^{-1} \)
Verified Correct Answer: D.
Physical Principles & Numerical Solution
From Newton's second law:
\( F = \frac{mV - mµ}{t} \)
Let the final velocity = V; and since the football is initially at rest, its initial vel µ = 0, M = 0.8kg
t = 0.8s
\(\implies 100 = \frac{0.8V - 0.8 \times 0}{0.8}\)
\(\text{Therefore } V = \frac{100 \times 0.8}{0.8} = 100ms^{-1}\)
Source: Myschool Past Questions Archive (Record #41456)