Answer to Question #308831 in Physics for Fish

Question

A 3.5kg block is pushed along a horizontal floor by a force F of magnitude 15N at an angle 40°W horizontal. The coefficient of kinetic friction between the block and the floor is 0.25. Calculate the magnitude of:

(a) frictional force on the block from the floor

(b) the block's acceleration

Answer 1

The Newton's second law says

$ma=F\cos40^\circ-F_f$

and

$N=mg-F\sin40^\circ\\ =3.5*9.8-15\sin40^\circ=24.7\:\rm N$

Hence:

(a) frictional force on the block from the floor

$F_f=\mu N=0.25*24.7=6.2\:\rm N$

(b) the block's acceleration

$a=(15\cos40^\circ-6.2)/3.5=1.5\:\rm m/s^2$