Science: Momentum and Collisions
Using mass, velocity, and conservation of momentum
Science: Momentum and Collisions
Using mass, velocity, and conservation of momentum
Science - Grade 9-12
- 1
A 2 kg cart moves to the right at 5 m/s. What is its momentum?
Use p = mv.
The cart's momentum is 10 kg m/s to the right because momentum equals mass times velocity, so 2 times 5 equals 10. - 2
A 1200 kg car is moving at 18 m/s east. Calculate its momentum.
The car's momentum is 21,600 kg m/s east because 1200 times 18 equals 21,600. - 3
A 0.50 kg soccer ball is kicked and moves at 16 m/s north. What is the ball's momentum?
Multiply mass by velocity and keep the direction.
The ball's momentum is 8.0 kg m/s north because 0.50 times 16 equals 8.0. - 4
A 1500 kg truck is initially at rest. After a force acts, it moves at 4 m/s west. What is its final momentum?
The truck's final momentum is 6000 kg m/s west because 1500 times 4 equals 6000. - 5
A 3 kg object changes velocity from 2 m/s east to 7 m/s east. Find the change in momentum.
Find initial and final momentum first, then subtract.
The change in momentum is 15 kg m/s east because the initial momentum is 6 kg m/s east, the final momentum is 21 kg m/s east, and 21 minus 6 equals 15. - 6
A 4 kg object moves at 6 m/s right and then at 2 m/s right after a collision. What is the object's change in momentum?
The change in momentum is -16 kg m/s, or 16 kg m/s to the left, because the momentum changes from 24 kg m/s right to 8 kg m/s right. - 7
A force of 12 N acts on an object for 0.50 s. What impulse does the object receive?
Use J = Ft.
The object receives an impulse of 6.0 N s because impulse equals force times time, so 12 times 0.50 equals 6.0. - 8
A 0.25 kg ball at rest is hit and leaves with a velocity of 20 m/s east. What impulse was delivered to the ball?
The impulse delivered to the ball is 5.0 N s east because impulse equals change in momentum, and the momentum changes from 0 to 0.25 times 20, which is 5.0. - 9
Two carts collide and stick together. Cart A has mass 2 kg and velocity 4 m/s right. Cart B has mass 3 kg and is at rest. What is their final velocity?
For objects that stick together, total momentum before equals total momentum after.
Their final velocity is 1.6 m/s to the right because the total initial momentum is 8 kg m/s right and the total mass after sticking is 5 kg, so 8 divided by 5 equals 1.6. - 10
A 1.5 kg cart moving at 6 m/s east collides with a 1.0 kg cart moving at 2 m/s east. They stick together. Find their final velocity.
Their final velocity is 4.4 m/s east because the total initial momentum is 9 plus 2, which is 11 kg m/s east, and the total mass is 2.5 kg, so 11 divided by 2.5 equals 4.4. - 11
A 0.20 kg puck moves at 10 m/s east and collides with a 0.30 kg puck moving at 4 m/s west. They stick together. What is their final velocity?
Choose one direction as positive and treat the other as negative.
Their final velocity is 0.8 m/s west because the total initial momentum is 2.0 east plus 1.2 west, which gives 0.8 kg m/s east overall if east is positive? No. Taking east as positive, the total momentum is 2.0 minus 1.2 equals 0.8 kg m/s east. Dividing by the total mass of 0.50 kg gives 1.6 m/s east. - 12
A 900 kg car traveling 20 m/s east collides head-on with a 1100 kg car traveling 10 m/s west. If they stick together, what is their final velocity?
Head-on collisions require careful attention to signs.
Their final velocity is 3.5 m/s east because the total initial momentum is 18,000 east minus 11,000 west, giving 7,000 kg m/s east. The combined mass is 2000 kg, so 7000 divided by 2000 equals 3.5. - 13
A 5 kg object has a momentum of 30 kg m/s north. What is its velocity?
Its velocity is 6 m/s north because velocity equals momentum divided by mass, and 30 divided by 5 equals 6. - 14
A 0.40 kg ball changes velocity from 3 m/s south to 7 m/s north. Find the impulse on the ball.
Treat opposite directions with opposite signs.
The impulse on the ball is 4.0 N s north if north is positive. The initial momentum is -1.2 kg m/s, the final momentum is 2.8 kg m/s, and the change is 4.0 kg m/s, which equals 4.0 N s. - 15
In one or two complete sentences, explain the law of conservation of momentum for a closed system.
The law of conservation of momentum states that the total momentum of a closed system stays constant if no external net force acts on it. Momentum can move from one object to another during a collision, but the total amount remains the same.