Momentum and Collisions

Question 1

what is linear momentum

Answer 1

the product of a bodies mass and velocity

Question 2

what is the formula for momentum

Answer 2

• momentum = mass x velocity

- p = mv

Question 3

what are the units of momentum

Answer 3

• kgms-1

- Ns

Question 4

is momentum a vector or a scalar

Answer 4

• a vector

- because it also has a direction

Question 5

how does momentum always behave in a closed system

Answer 5

it is conserved

Question 6

what does the conservation of momentum mean

Answer 6

• that the total momentum before and event is equal to the total momentum after an event
• as long as the momentum is elastic, the difference between the magnitudes of the momentum before and after will be 0

Question 7

if you had an object travelling at a velocity which then hits an object in front and they now move together, what would you expect to happen to the velocity of the combined objects

Answer 7

• the velocity would decrease
• as with the two objects moving together, their total mass has increased
• and a momentum is conserved, the velocity must decrease in order for the momentum after the event to be the same as before

Question 8

what is a typical question which uses the idea of objects combining to make a new mass

Answer 8

• an arrow travelling at a constant velocity hitting a wooden box
• the mass of the arrow and the box are added a it acts as one object now
• leading to the velocity of that new object being less than the velocity of the arrow before the event

Question 9

what condition has to be met in order for the conservation of momentum to be true

Answer 9

no external forces must be acting on the objects in the system

Question 10

what must you remember when calculating momentum of objects colliding from opposite directions

Answer 10

• that one would be assigned a positive momentum and the other would be assigned a negative
• because it is a vector, so one of them would need to have a negative direction
• as one of the velocities would be negative