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JAMB Physics 2011 Paper

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Question : 3

Total: 44

If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?

90 m
30 m
45 m
60 m

Solution:

Concept:

For a body falling freely from rest, the distance covered is

s = \frac{1}{2}gt^2

.

Explanation:

The object starts from rest, so initial velocity

u = 0

.

Using the equation

s = ut + \frac{1}{2}gt^2

, we have:

s = 0 \times t + \frac{1}{2}gt^2 = \frac{1}{2}gt^2

.

Given

t = 3\text{ s}

and taking

g = 10\text{ m/s}^2

:

s = \frac{1}{2} \times 10 \times (3)^2

s = 5 \times 9 = 45\text{ m}

.

Answer:

The distance covered is

45\text{ m}

, i.e. option C.

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