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JAMB Physics 2017 Paper

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Question : 29

Total: 49

A constant force of 5N acts for 5 seconds on a mass of 5kg initially at rest. Calculate the final momentum

125kgms−1
25kgms−1
15kgms−1
0kgms−1

Solution:

Concept:

Impulse of a force equals the change in momentum of the body.

Explanation:

The body starts from rest, so its initial velocity is

u = 0

.

Impulse

= F t

.

Change in momentum

= m v - m u

.

So,

F t = m v - m u

.

Substitute the values:

F = 5\,\mathrm{N}

,

t = 5\,\mathrm{s}

,

m = 5\,\mathrm{kg}

, and

u = 0

.

5 \times 5 = 5v - 5(0)

.

25 = 5v

.

Therefore,

v = 5\,\mathrm{m/s}

.

Final momentum

= m v = 5 \times 5 = 25\,\mathrm{kg\,m\,s^{-1}}

.

The correct option is B.

Answer:

25\,\mathrm{kg\,m\,s^{-1}}

(Option B).

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