Topic 2.3: Momentum and Impusle Flashcards
What is the formula for MOMENTUM?
momentum = mass * velocity
What is needed to change momentum?
A force is needed to change momentum
What is the relationship between force direction and the change in momentum direction?
The force direction is the same as the change in momentum direction
What is the formula for IMPULSE?
Impulse = Force * contact time = change in momentum
What does the kinetic theory of gases say about bouncing molecules?
Kinetic theory of gases says no energy is lost in colliding with the wall (or other molecules)
Bounce velocity has the same magnitude as impact velocity
What is the conservation of linear momentum?
In any collision or explosion, for an isolated system with no external force acting; the total momentum before the collision (or explosion) is equal to the total momentum after the collision (or explosion), or change in momentum = 0
What is ELASTIC COLLISION?
Kinetic Energy is conserved (ie same total value before and after collision)
What is INELASTIC COLLISION?
Kinetic Energy is not conserved
What is COMPLETELY INELASTIC COLLISION?
Kinetic Energy is not conserved and the masses stick together
How do rockets take off?
A rocket exerts a force, Frg, on exhaust gases backwards. This force is due to changing the momentum of the gas from zero to mv
A mass of gas is ejected per second at constant velocity
Frg is the force that causes the rocket to accelerate
same physics applies to hovercraft, helicopters, etc, if they are vertically stationary
What is the kinetic energy and momentum formula?
E = p² / 2m
kinetic energy = momentum² / (2 * mass)
When can the KINETIC ENERGY AND MOMENTUM formula be used?
The equation can only be used at non-relativistic velocities.
That is well below the speed of light, so that mass is constant
