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JAMB Physics 2019 Paper

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Question : 37

Total: 100

A force of 6N acts horizontally on a stationary mass of 2kg for 4s. The kinetic energy gained by the mass is _________

366j
240j
144j
90j

Solution:

Concept:

Kinetic energy gained equals the work done by the force, or the energy acquired from rest due to the applied force.

Explanation:

Given:

F = 6\,\text{N}

,

m = 2\,\text{kg}

,

t = 4\,\text{s}

, and initial velocity

u = 0

.

Use the impulse-momentum relation:

Ft = m(v - u)

.

Since

u = 0

,

v = \frac{Ft}{m}

.

Substitute values:

v = \frac{6 \times 4}{2} = \frac{24}{2} = 12\,\text{m/s}

.

Kinetic energy is

KE = \frac{1}{2}mv^2

.

So,

KE = \frac{1}{2} \times 2 \times (12)^2 = 1 \times 144 = 144\,\text{J}

.

Answer:

144\,\text{J}

, which is option C.

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