81-83 - Power + Momentum Flashcards
What is power?
How much work is done per second
How is power measured?
In watts or J/s
How do you find power?
Work done or energy transferred / time
What is the equation for momentum?
Momentum = mass * velocity
P = m*v
Is momentum a vector or scalar quantity and why?
Vector - it has a direction
What is the conservation of momentum rule?
Momentum before = momentum after collision
Why does a gun recoil when fired?
The initial momentum of 0 must be balanced out
What causes a change in momentum?
A force
What happens to kinetic energy when brakes are applied?
It is transferred into heat and sound energy
What do regenerative braking systems do?
Reverse motor to slow wheels, motor converts kinetic energy into electrical, stored in battery as chemical
Why are car crashes so dangerous?
Big change in momentum, short amount of time = high forces
How do crumple zones work?
The kinetic energy is converted as the car body changes shape, increasing impact time
How do seat belts work?
They stretch, increasing time it takes for wearer to stop
Absorb some of the kinetic energy when stretching
What do side impact bars do?
Direct some kinetic energy away from the passengers
How do air bags work?
Make you take more time to stop
Prevent you from hitting hard surfaces
