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ICSE Class 10 Physics Question 1 of 23

Work, Energy and Power — Question 10

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Question

Question 10

Assertion (A): When the displacement is normal to the direction of force, the work done is zero.

Reason (R): Work done depends on the angle between force and displacement.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not the correct explanation of A
  3. assertion is false but reason is true
  4. assertion is true but reason is false
Answer

Both A and R are true and R is the correct explanation of A.

Explanation

Assertion (A) is true.

As,

Work done (𝑊) =𝐹⃗\vec𝐹⋅𝑑⃗\vec𝑑= Fdcosθ .............(i)

Where

F = magnitude of force

d = displacement

θ = angle between force and displacement

If displacement is normal (perpendicular) to the force, then 𝜃 = 90o90^o

⇒\Rightarrow cos 90o90^o = 0 ⇒\Rightarrow W = 0

Reason (R) is true.

From (i) it is clearly visible that work done depends upon angle between force vector and displacement vector.

Hence, R is the correct explanation of A.