A person pushes a 16.0 kg lawn mower at constant speed with a force of 83.0 N di

Question

A person pushes a 16.0 kg lawn mower at constant speed with a force of 83.0 N directed along the handle, which is at an angle of ? = 40.0° to the horizontal (Fig. 4-40).(a) Draw the free-body diagram showing all forces acting on the mower. (Do this on paper. Your instructor may ask you to turn in this diagram.)
(b) Calculate the horizontal retarding force on the mower
63.582 N
(c) Calculate the normal force exerted vertically upward on the mower by the ground.
210.311 N
(d) Calculate the force the person must exert on the lawn mower to accelerate it from rest to 0.8 m/s in 2.0 seconds (assuming the same retarding force).
???????????? N

Explanation / Answer

b) From free body diagram Fcos@ - Fp = ma = 0 ==> Fp = F cos@ = 83 * cos40 = 63.58 N c) Normal force Fn = F sin@ + m g = 83 * sin40 + 16 * 9.8 = 53.35 + 156.8 = 210.15 N d) acceleration a = v / t = 0.8 / 2 = 0.4 m/s^2 ==> F cos40 - Fp = ma ==> F = [Fp + m a ] / cos40 = [63.58 + 16 * 0.4 ] / cos40 = 91.352 N

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