General Science - Physics (Basics)
Two objects of masses 3 kg and 6 kg are moving with velocities 4 m/s and 2 m/s respectively in the same direction. What is the net force required to stop both in 2 seconds?
Two objects of masses 3 kg and 6 kg are moving with velocities 4 m/s and 2 m/s respectively in the same direction. What is the net force required to stop both in 2 seconds?
hard Q9 of 15
Step-by-Step Solution
Step 1: Calculate initial momentum of each object
Momentum = mass × velocity. For 3 kg: 3 × 4 = 12 kg·m/s; for 6 kg: 6 × 2 = 12 kg·m/s.Step 2: Total momentum and change in momentum
Total momentum = 12 + 12 = 24 kg·m/s. To stop, final momentum = 0, so change = 24 kg·m/s.Step 3: Calculate net force
Force = change in momentum / time = 24 / 2 = 12 N. But force acts on both objects separately, so total force = force on 3 kg + force on 6 kg.Step 4: Calculate force on each object
Force on 3 kg = (3 × 4) / 2 = 6 N; force on 6 kg = (6 × 2) / 2 = 6 N; total force = 6 + 6 = 12 N.Step 5: Re-examine options
12 N is total force to stop both objects in 2 seconds.Final Answer:
12 N → Option BQuick Check:
Force = total momentum change ÷ time = 12 N ✅
Quick Trick: Calculate force for each object and sum for total force.
Common Mistakes:
MISTAKES- Adding velocities or masses incorrectly or ignoring time.
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