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)