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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Work and Energy

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Work and Energy

A block of mass 1 kg is positioned at point A on a rough track, as...

A block of mass 1 kg1\text{ kg} is positioned at point AA on a rough track, as shown in the figure. When given a slight push to the right, it comes to rest at point BB on the track. Determine the work done by the frictional force on the block during its journey from AA to BB.
A block of mass 1 kg is positioned at point A on a rough track, as shown in the figure. When given a slight push to the

Options

  1. A2 J2\text{ J}
  2. B−2 J-2\text{ J}
  3. C−10 J-10\text{ J}
  4. D−8 J-8\text{ J}

Correct answer

B. −2 J-2\text{ J}

Step-by-step solution

Using the work-energy theorem:

Wnet=ΔKW_{\text{net}} = \Delta K

Wgravity+Wfriction=KB−KAW_{\text{gravity}} + W_{\text{friction}} = K_B - K_A

Since the block starts from rest (given a slight push) and comes to rest at BB, KA=0K_A = 0 and KB=0K_B = 0.

The work done by gravity is:

Wgravity=mg(hA−hB)W_{\text{gravity}} = mg(h_A - h_B)

Substituting m=1 kgm = 1\text{ kg}, g=10 m/s2g = 10\text{ m/s}^2, hA=1.0 mh_A = 1.0\text{ m}, and hB=0.8 mh_B = 0.8\text{ m}:

Wgravity=1×10×(1.0−0.8)=2 JW_{\text{gravity}} = 1 \times 10 \times (1.0 - 0.8) = 2\text{ J}

Therefore, the work-energy equation becomes:

2+Wfriction=02 + W_{\text{friction}} = 0

Wfriction=−2 JW_{\text{friction}} = -2\text{ J}
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