Answer to Question #326264 in Mechanics | Relativity for Anonymous005

Question

A squash ball hits a wall with an initial speed of u and it rebounds in the opposite direction with speed v. Knowing that some energy has been lost through heat in the collision so that v < u and that the duration of the collision is t, find the magnitude of the average force exerted by the wall on the ball.

a) F = m(u+v)/t

b) f = m(u-v)/t

c) F = 0

d) F = m(2v-u)/t

Answer 1

Let's use second Newton's law $F=ma$ ,

where F and a are average values and let's select positive direction along force;

in this coordinates velocity before collision will be negative

$a=\frac{\Delta v}{t}=\frac{v-(-u)}{t}=\frac{u+v}{t}\\ F=\frac{m(u+v)}{t}$

Answer: a)