A woman pushes a lawnmower forward with a force of 125 N for a distance of 15 m

Question

The force makes an angle of 34° with the horizontal. At the same, a constant 50.0N frictional force on the lawn mower from the ground opposes the motion. Calculate the total amount of work done on the lawn mower.

Answer 1

Work = Force * Distance * cos("angle between Force and Distance")

There are 4 forces acting on the lawnmower: Applied force (F=125N), Kinetic friction (f=50N), Weight, and Normal.

There is no work due to weight and normal forces because the angle between the distance and force vectors is 90 degrees. And cos(90º)=0. Work can only be done when force and distance are along the same axis.

Work due to applied force = (125N)*(15m)*cos(34º)

Work due to kinetic friction = (50.0N)*(15m)*cos(180º)

Friction opposes the direction of motion, so the angle between friction and distance is 180º. cos(180º)=-1, so the work due to friction will always be negative.

Add both works together to solve the total work done on the lawnmower.

Work=804N