Question

Assertion: A person working on a horizontal road with a load on his head does no work. Reason: No work is said to be done, if directions of force and displacement of load are perpendicular to each other.


1) If both assertion and reason are true and the reason is the correct explanation of the assertion.

2) If both assertion and reason are true but reason is not the correct explanation of the assertion.

3) If assertion is true but reason is false.

4) If the assertion and reason both are false.

5) If assertion is false but reason is true.

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Answer 1

Answer:

option A

Explanation:

The work done W=F.s=Fcosθ when a person walk on a horizontal road with load on his head then θ=90 degree

hence W=Fcos90 degree=0

Thus no work is done by the person.

Answer 2

$\LARGE{ \underline{ \blue{ \sf{Required \: answer:}}}}$

We know,

Work is said to be done when a force applied on a body causes some displacement. And mathematically, it is given by:

$\large{ \boxed{ \sf{W = Fs \cos( \theta) }}}$

Here, W is the work done, F is the force applied and s is the displacement of the body. Cos theta is the cosine of angle between them.

Here,

The load is applying force on the downward directions and displacement is in the forward direction. As they are perpendicular to each other, the angle is 90°.

We know that, Cos 90° = 0

Then,

⇛ W = Fs × cos 90°

⇛ W = Fs × 0

⇛ W = 0

Thus, Work done by the person is 0.

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According to our approach, Work done by the person is 0 when the person is carrying the load and walking in a horizontal road. Hence, assertion is correct✓.

And this is due to the angle between force on head and displacement, which is equals to 90°. And cos 90° is 0, hence work done is 0. So, reason is also correct✓ and is the correct explanation of assertion.

Thus, Correct option is Option (1)