Solution to problems – class 9 physics – Set 1 Q 55
Last updated on January 2nd, 2020 at 07:55 am
Problem Statement
55) A girl of mass 50 kg jumps out of a rowing boat of mass 300 kg on to the bank, with a horizontal velocity of 3 m/s. With what velocity does the boat begin to move backwards ?
Solution
As no initial velocity is given in the
problem statement, we will consider it as zero.
So whatever movement the boat gets its due to the jump of the girl.
So initial momentum =0
Mass of the girl =m1 =50 kg
velocity of the girl =v1 = 3 m/s
Mass of the boat =m2 =300 kg
Velocity of the boat =v2 =?
Final momentum = m1v1 + m2v2 =50 x 3 + 300 v2
As per the law of conservation of
momentum,
150 + 300v2 = 0
Or, v2 = -150/300 = -0.5 m/s
The negative sign indicates that the boat go backwards
Go back to the 101 problems set (class 9)
Problems Set – grade 9
