Verified Solution • 2025–26 Session
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Q4.23: NCERT Physics - Part 1 LAWS OF MOTION 4.23 Solution: Explain why (a) a horse cannot pull a cart and run in empty…
⚠️ Common Exam Traps & Conceptual Pitfalls
Students often think pulling is easier because the force is applied at a lower point, but the real reason is that pulling introduces a downward component that reduces the normal force $N$ and thus the friction $f=mu N$. Pushing adds an upward component, increasing $N$ and friction. Always check how the applied force changes $N$ before deciding which is easier.
Explain why (a) a horse cannot pull a cart and run in empty space, (b) passengers are thrown forward from their seats when a speeding bus stops suddenly, (c) it is easier to pull a lawn mower than to push it, (d) a cricketer moves his hands backwards while holding a catch.
Step-by-Step Verified Solution
**Answer:** (a) Horse needs ground for friction to push against (b) Inertia of motion (c) Pulling reduces normal force and friction (d) Increases time to reduce force
**Step-by-Step Explanation:**
(a) The horse pushes the ground backward, and the ground pushes the horse forward (Newton's third law). In empty space, there is no ground to push against [citation:11].
(b) When the bus stops suddenly, the lower part of the passenger's body stops with the bus, but the upper part continues forward due to inertia of motion [citation:11].
(c) When pulling, the vertical component of the applied force reduces the normal force, hence reducing friction. When pushing, the vertical component increases the normal force and friction [citation:10].
(d) By moving hands backward, the cricketer increases the time of impact. Since impulse = F _ t, a longer time means a smaller force on the hands [citation:11].
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