Question

an observer and a vehicle both start moving together from rest with acc 5 m/s^2 and 2 m/s^2 in same directions .there is a 2 kg block on the floor of the vehicle and coeff of friction is 0.3 betwwen their surfaces . find the work done by the frictional force on the block as observed by the running observer during first 2 secinds of motion ?

Answer 1

The relative acceleration for the car is :

Acceleration = 5 - 2 = 3 m/s²

The block is also moving with the same acceleration.

The frictional force equals :

F = ωma

Where :

m = mass

ω = coefficient of kinetic friction.

a = acceleration due to gravity.

Now doing the substitution we have :

F = 0.3 × 3 × 2 = 1.8 N