Question

A girl in a canoe uses a paddle to push the canoe at rest from a dock giving it a speed of 0.30 m/s. If the paddle is in contact with the dock for 0.75 seconds, what is the average force on the canoe? (The mass of the canoe is 27 kg and the girl is 52 kg)

Answer 1

Canoe will start from rest and reach to speed v = 0.30 m/s

so here we will have

$v_i = 0$

$v_f = 0.30 m/s$

now in this speed increase it will take 0.75 second of time

so we can find the acceleration of canoe as we know that acceleration is rate of change in velocity

$a = \frac{v_f - v_i}{t}$

$a = \frac{0.30 - 0}{0.75} = 0.4 m/s^2$

now we can find the force on Canoe by using Newton's II law

$F = ma$

here m = mass of girl + mass of canoe

m = 27 + 52 = 79 kg

now by above formula

$F = 79 * 0.4 = 31.6 N$

so here it will have net force F = 31.6 N