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Q · Newton's Laws of MotionMedium · 45s
A car moving at 20 m/s stops in 4 seconds. The average retarding force if the mass is 1000 kg is:
TopicNewton's Laws of Motion
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
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Initial momentum = 1000 × 20 = 20000 kg m/s Final momentum = 0 Force = Δp/Δt = -20000/4 = -5000 N (retarding). Magnitude is 5000 N. Correction: Wait! Should be: F = ma a = Δv/Δt = 20/4 = 5 m/s², but negative. So, F = 1000×5 = 5000 N.
Final Answer: Option B — 5000 N