A 60 kg man stands in a stationary 240 kg boat holding a 0.5 kg sphere. He throws it horizontally at speed 12 m/s. If boat’s recoil speed is n×10⁻² m/s, find n.
Physics · Mixed Chapter
JEE Main Practice

Question

A 60 kg man stands in a stationary 240 kg boat holding a 0.5 kg sphere. He throws it horizontally at speed 12 m/s. If boat’s recoil speed is n×10⁻² m/s, find n.

G1 Physics · Accepted Answer

Step 1: Initial horizontal momentum is zero. Step 2: Taking throw speed approximately relative to shore, recoil momentum of boat+man has magnitude ≈0.5×12=6 kg·m/s. Step 3: Their combined mass ≈60+240=300 kg, so recoil speed≈6/300=0.02 m/s. Step 4: 0.02=2×10⁻²; n=2. (Exactly, if 12 m/s is relative to thrower, result differs by <1%.)