Question

A girl scout paddling a canoe pushes the water back with her paddle, exerting a backward force of 170 N on the water. Find the acceleration of the girl and the canoe if their combined mass is 75.0 kg. (Let forward be the positive direction. Indicate the direction with the sign of your answer.)

Answer 1

Solution:

Using the Newtons third law,

Every action has an equal and opposite reaction.

The girl pushes the water back with a force of 170 N.

So the water will push the girl forward with the same force (170 N) since every action has an equal and opposite reaction.

So the girl will accelerate in the forward direction.

F_net = +170

ma = +170

a = +170/75

= +2.26667 m/s²

= +2.3 m/s².

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