Chapter - 2 Force and Laws of Motion

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Q
Force and Laws of Motion

Question:

How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Take its downward acceleration to be 10 ms^{-2} .

Answer:

Given: Mass of the dumb-bell (m) = 10 kg

Distance covered (s) = 80 cm = 0.8 m

Initial velocity (u) = 0 (it is dropped from a position of rest)

Acceleration (a) = 10 ms^{-2}

Final velocity (v) =?

Using the third equation of motion,

v^2 - u^2 = 2as

v^2 - (0)^2 = 2 	imes 10 	imes 0.8

v^2 = 16 ms^{-1}

v = 4 ms^{-1}

V = 4 m/s

Momentum of the dumb-bell when it hits the ground = mv

Momentum of the dumb-bell when it hits the ground = 10 	imes 4 = 40 kgms^{-1}

The momentum transferred by the dumb-bell to the floor is 40 kgms^{-1}


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