# chapter 9 momentum Flashcards

momentum equation

momentum p = mass (kg) * velocity (ms^-1)

what would happen when a ball(1) of velocity v with mass m hits a stationary ball(2) of the same mass

ball(1) would stop on impact, ball (2) would move off with the same velocity v, conserving momentum

what would happen when a ball(1) of velocity v with mass m hits a stationary ball(2) that is much heavier

ball(1) would rebound off of it, while ball(2) would move only a bit slowly as a response

how is momentum conserved in collisions and explosions

the momentum before is the same as the momentum after

mass before * velocity before = mass after * velocity after

is momentum a vector or scalar

vector, the equation for momentum contains velocity, which is a vector

use the equation ‘mv’ to show conservation of momentum between a ball of velocity v hitting a stationary ball, both have same mass

mv + 0 = mv –> 0 + mv = mv

state newton’s first law - the law of inertia

a body stay at rest, or continue to accelerate at a constant acceleration, unless acted upon by an external force

state Newton’s second law - the law of force

the acceleration of an object is directly proportional to the force applied (F = ma).

how does Newton’s second law apply to momentum

the rate of change of momentum is directly proportional to the force

F = Δp / Δt = ma

Δp = mΔv

what is impulse of a force

the force multiplied by the time the force is applied for, so impulse is equal to the change in momentum

Δp = FΔt

how do you increase impulse

increase the force, or the time it acts for

how are crumple zones in cars used for improved driver safety

they reduce the force on the driver

as momentum is constant, and Δp = FΔt

crumple zones increase the duration of the crash, so change in time increases, but to keep change in momentum constant, the force decreases so the force on the passenger decreases, improving their safety

how do seat belts air bags improve safety

they reduce the force on the driver

as momentum is constant, and Δp = FΔt

seat belts stretch slowly and air bags deflate gradually, increasing how long it takes for a person to come to a halt if the car comes to a halt

how do you get impulse from a force-time graph

the area under a force time graph between 2 points on the X-axis give the impulse

what does area under a graph of force-time give

impulse (change in momentum)