A body is moving with a speed of 1ms⁻¹ and a force F is needed to stop it in a distance x. If the speed of the body is 3 ms⁻¹, the force needed to stop it in the same distance x will be:
Correct answer: D. 9 F
- A. 1.5 F
- B. 3 F
- C. 6 F
- D. 9 F
Explanation
Work done by the stopping force equals change in kinetic energy, which ∝ v². Increasing speed from 1 to 3 multiplies K.E by 9, so the required stopping force (same stopping distance) must be 9 times larger: 9F.
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Displacement, velocity and acceleration describe motion, including the horizontal and vertical components of projectile motion. The chapter connects these quantities with Newton's laws, momentum and impulse, then applies conservation of momentum to collisions, distinguishing elastic collisions from inelastic ones.
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