Chapter 18: Momentum Flashcards
How do you calculate momentum?
Momentum = mass x velocity
What is the principle of the conservation of momentum?
For a system of interacting objects, the total momentum remains constant, provided no external force acts on the system.
What is Newton’s Third Law?
If object A exerts a force on object B, the object B exerts and equal and opposite force on object A.
What is an elastic collision?
In an elastic collision, momentum and kinetic energy are both conserved.
What is an inelastic collision?
In an inelastic collision, momentum is conserved, but kinetic energy is not.
How do you work out the recoil velocity of a weapon?
Velocity = momentum of bullet/mass of weapon
Is momentum a vector or a scalar quantity?
Momentum is a vector.
Why do guns have recoil?
Guns have recoil because momentum is conserved. The bullet started off with a momentum of zero, and so as it has a sudden increase to the right, therefore the gun must have an equal and opposite reaction.
Explain how seat belts help protect you in a car.
Seat belts, whilst they stop you from falling around, are designed to stretch a little, so that there is time for your body’s momentum to reach zero, and so reduces the forces on it.
Explain how air bags help protect you in a collision.
They increase the time taken for your head’s momentum to reach zero, thereby reducing the force on it. They also act as a soft cushion and can prevent cuts.
What is the equation linking force and momentum?
Force = change in momentum/Time taken
