Advertisements
Advertisements
Question
A girl riding a bicycle along a straight road with a speed of 5 ms–1 throws a stone of mass 0.5 kg which has a speed of 15 ms–1 with respect to the ground along her direction of motion. The mass of the girl and bicycle is 50 kg. Does the speed of the bicycle change after the stone is thrown? What is the change in speed, if so?
Solution
Given, the total mass of girl, bicycle and stone = m1 = (50 + 0.5) kg = 50.5 kg.
Velocity of bicycle u1 = 5 m/s, Mass of stone m2 = 0.5 kg
Velocity of stone u2 = 15 m/s, Mass of girl and bicycle m = 50 kg
Yes, the speed of the bicycle changes after the stone is thrown.
Let after throwing the stone the speed of bicycle is v ms.
According to the law of conservation of linear momentum,
m1u1 = m2u2 + mv
50.5 × 5 = 0.5 × 15 + 50 × v
252.5 – 7.5 = 50 v
or v = `245.0/50`
v = 4.9/m/s
Change in speed = 5 – 4.9 = 0.1 m/s.
APPEARS IN
RELATED QUESTIONS
Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s−1 and 1 m s−1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s−1. Determine the velocity of the second object.
A shell of mass 0.020 kg is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 m s–1, what is the recoil speed of the gun?
Explain how, a karate player can break a pile of tiles with a single blow of his hand.
Calculate the momentum of a toy car of mass 200 g moving with a speed of 5 m/s.
A plastic ball and a clay ball of equal masses, travelling in the same direction with equal speeds, strike against a vertical wall. From which ball does the wall receive a greater amount of momentum ?
A man throws a ball weighing 500 g vertically upwards with a speed of 10 m/s.
- What will be its initial momentum ?
- What would be its momentum at the highest point of its flight ?
A body of mass 2 kg is at rest. What should be the magnitude of force which will make the body move with a speed of 30 m/s at the end of 1 s ?
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 ?
A truck of mass 500 kg moving at 4 m/s collides with another truck of mass 1500 kg moving in the same direction at 2 m/s. What is their common velocity just after the collision if they move off together ?
The rockets work on the principle of conservation of :
