Answer:
A manually-operated lawn mower needs a lot of force to move. The mower mechanism and the energy needed to cut through the grass causes a lot of friction. In order to cut the grass faster, you need to overcome all that friction and get a net positive force on the lawn mower. Thus, you need to apply more force to it. It also helps a lot to reduce friction, so oil the mower and keep the blades sharp.
Explanation:
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