A man pushes a 16 kg lawn mower at a constant speed with a force F =
90 N directed along the handle, which is at an angle of 45° to the
horizontal (see below). Calculate:

a.the horizontal retarding force on the mower;


b.the normal force exerted vertically upward on the mower by the
ground; and


c.the force the man must exert on the lawn mower to accelerate it from
rest to 1.5 ms-1 in 2.5 seconds. Assume the same retarding force.

a) retarding force is the same as the horizontal force exerted by the
man, that is 90/sqrt(2) N.  64 N

b) the weight of the mower (16kg * 9.8 N/kg) plus the vertical force
exerted by the man, which is 90/sqrt(2) N.  220 N

c) net force is mass*acceleration.  acceleration = 1.5/2.5 m/s^2 = .6
m/s^2, so net force is .6 m/s^2 * 16 kg = 9.6 N.  In addition there is
90/sqrt(2) N retarding force.  73 N