Question

A gardener pushes a lawnmower of mass 18kg at a constant speed. To do this requires a force P of 80N directed along the handle, which is at an angle of 40°to the horizontal.

a) Calculate the horizontal frictional force

b) If this frictional force were constant, what force, applied along the handle, would accelerate the mower from rest to 1.2m/s in 2.0s?

Answer 1

a) $f=P\cos\theta=61.3\text{ N}.$

b) By Newton's second law:

$$F=\dfrac{ma+f}{\cos\theta}=\dfrac 1{\cos\theta}\bigg(\dfrac{vm}{t}+f\bigg),\\\space\\ F=94\text{ N}.$$