Question

A heavy box is slid across a rough floor with an initial speed of 4m/s. It stops moving after 8 seconds. If the average resisting force of friction is 10N, the mass of the box (in kg)is?

Answer 1

u=4m/s
t=8s
v=0

now , v=u+at
0=4+8a
a=1/2 m/s2 ---(1)

Now F=ma
taking F as frictional force ,
10=m x 1/2
m=20kg