Chapter 3 - Work, Energy And Momentum Flashcards
What is gravitational potential energy
Energy stored in an object which depends on its weight and how far it moves vertically
What is the equation for gravitational potential energy
Ep= m x g x h
Ep= change in gravitational potential energy (J) M= mass (kg) G= gravitational field strength (N/kg) H= change in height (m)
What is the equation for power
P= E
____
t
P= power (w) E= energy (J) T= time (s)
What does kinetic energy depend on
The mass and speed
What is the equation for kinetic energy
Ek= 1 x m x v2
__
2
Ek= kinetic energy (J) M= mass (kg) V= speed (m/s)
What is elastic potential energy
The energy stored in an elastic object when work is done on the object
What does momentum depend on
Mass and the velocity of an object
What is the equation for momentum
P= m x v
P= momentum (kg m/s) M= mass (kg) V= velocity (m/s)
What is the law of conversation of momentum
Whenever objects interact, the total momentum before the interaction is equal to the total momentum afterwards, provided no external forces act on them
Why is the momentum zero after an explosion
The objects move apart with equal and opposite momentum. One momentum is positive, the other negative so the total momentum after the explosion is zero.
What is the impact time
The time taken for a collision to take place
What are the purposes of crumple zones
To fold in a collision. This increases the impact time and so reduced the force on the car and people in it
Name a number of safety features designed to reduce the forces on the occupants of a car in a collision
- Side impact bars and crumple zones fold up in a collision to increase impact time.
- Seat belts and air bags spread the forces on the body across a larger area.
How do you find the speed of a car before an impact
By using the conservation of momentum
What is the equation for work done
W= f x d
W= work done (J) F= force (N) D= distance (m)
