Laws Of Motion Test

Result

Laws Of Motion Test - 9

Score
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Rank
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TIME Taken - -

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Question 1
1 / -0

A monkey of mass 20 kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it, but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope? (g = 10 m/s²)

A
5.5 m/s²

B
2.5 m/s²

C
5 m/s²

D
10 m/s²

Solution

R = m (g + α)
250 = 20 (10 + α)
α = 2.5 m/s2
Question 2
1 / -0

N bullets, each of mass m kg, are fired with velocity v ms^-1 at the rate of n bullets per second upon a wall. The reaction offered by the wall to the bullets is

A
nNmv

B
Nmv/n

C
Nmn/v

D
nNv/m

Solution

The reaction force offered by the wall to the bullets = the force exerted by bullets on the wall (third law of motion) = the rate of change of momentum of bullets (second law of motion)
Now, total mass of n bullets = Nm. Momentum of n bullets = Nmv
If n bullets are fired per second, the change of momentum per second = nNmv