After jumping from a boat weighing 100 kg, a boy weighing 50 kg acquired a horizontal
August 23, 2021 | education
| After jumping from a boat weighing 100 kg, a boy weighing 50 kg acquired a horizontal speed of 10 m / s. How fast will the boat gain?
ml = 100 kg.
mm = 50 kg.
Vm “= 10 m / s.
Vl “-?
Rm + Rl = Rm “+ Rl” – the law of conservation of momentum for a closed boy-boat system.
ml * Vl + mm * Vm = ml * Vl “+ mm * Vm”.
Since before the jump the boat with the boy was at rest, then Vl = Vm = 0 m / s.
0 = ml * Vl “+ mm * Vm”.
ml * Vl “= – mm * Vm”.
Vl “= – mm * Vm” / ml.
Vl “= – 50 kg * 10 m / s / 100 kg = – 5 m / s.
The “-” sign indicates that after the jump, the boat began to move in the opposite direction of the boy’s jump.
Answer: after the jump, the boat began to move in the opposite direction of the boy’s jump at a speed Vl “= 5 m / s.
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