Work done by a force is zero when the angle between force and displacement is MCQ with Answer and Explanation

Work done by a force is zero when the angle between force and displacement is
A. 90°
B. 45°
C. 180°
D.
Answer: Option A
Solution (By JKSSB Mock Tests)
W = Fd cosθ, cos90° = 0, so work zero. e.g., coolie carrying load horizontally.

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Practice More Physics Questions

Question #1
In the equation F = ma, if mass is doubled and acceleration is halved, force becomes
A. Four times
B. Half
C. Double
D. Same

Correct Answer: Option D


Explanation:
F = m×a. New force F' = (2m)×(a/2) = m×a = F. So force remains unchanged. This is direct proportionality. Understand the relationship: doubling mass doubles force, halving acceleration halves it, net effect no change.

This question belongs to: Science Physics
Question #2
The energy possessed by a body due to its position or configuration is called
A. Thermal energy
B. Nuclear energy
C. Potential energy
D. Kinetic energy

Correct Answer: Option C


Explanation:
Potential energy: gravitational (mgh), elastic (½kx²). Kinetic energy due to motion. Total mechanical energy sum conserved in conservative forces.

This question belongs to: Science Physics
Question #3
The velocity-time graph of a particle moving in a straight line is shown. The displacement of the particle from t=0 to t=4s is: [Graph: triangle from (0,0) to (2,10) to (4,0)]
A. 30 m
B. 40 m
C. 10 m
D. 20 m

Correct Answer: Option D


Explanation:
Displacement = area under velocity-time graph. The graph forms a triangle with base 4 s and height 10 m/s. Area = ½ × base × height = ½ × 4 × 10 = 20 m. Since velocity is always positive, displacement equals distance travelled. Graphical analysis is powerful: area gives displacement, slope gives acceleration. This triangle represents motion with uniform acceleration followed by uniform retardation. Exam tip: For piecewise linear v-t graphs, calculate area of each geometric segment separately. Such graph-based questions assess conceptual clarity in motion analysis.

This question belongs to: Science Physics