Momentum

Question 1

What’s the formula used to calculate momentum?

Answer 1

momentum = mass x velocity or p = m x v

Question 2

What is meant by ‘conservation of momentum’?

Answer 2

In a closed system, the total momentum before an event is the same as the total momentum after the event

Question 3

The momentum of a seed pod before it explodes is zero. If momentum is conserved, what will the total momentum be after the explosion event?

Answer 3

Zero

Question 4

Calculate the momentum of a 120000 kg blue whale that is swimming at 5 m/s

Answer 4

600,000 kg m/s

p = m x v, so the whale’s momentum is 120000 x 5 = 600000 kg m/s

Question 5

Orla is cycling on her 10 kg bike at 6 m/s. The total momentum of Orla and her bike is 420 kg m/s. Calculate Orla’s mass

Answer 5

60 kg
m = p / v, so the mass of Orla and the bike is 420 / 6 = 70kg
Orla’s mass is 70 - 10 = 60kg

Question 6

Felipe is moving horizontally at u m/s when he lands on a stationary skateboard. Felipe and his skateboard move off at v m/s. Explain why u>v. Assume that Felipe and the skateboard form a closed system

Answer 6

Felipe and his skateboard form a closed system, so the total momentum of Felipe on his skateboard is equal to Felipe’s momentum before he landed on the skateboard. The combined mass of Felipe and his skateboard is greater than his mass alone, so for momentum to be conserved there must be a decrease in velocity.