Acceleration of a block due to friction?

Question

A horizontal force of 40 N is applied to a block of wood of weight 100 N lying on a rough, horizontal plane. If the coefficient of friction between the wood and the rough surface is 0.3, what is the acceleration of the block?

Do I use f = ma - umg?

Answer 1

Forward force = 40 N

Resistive frictional force = 100*0.3 = 30 N

Net resultant force = 40 - 30 = 10 N

Acceleration

= net force / mass

= 10/(100/9.8)

= 0.98 m/s^2.