2-Energy Flashcards
What is the equation for work done?
Work done=Energy transferred
OR
Work done=Force appliedxDistance moved
What is energy measures in?
Joules (J)
What two things does the kinetic energy of an object depend on?
Mass (kg)
Speed (m/s)
What is the weight of an object?
The force of gravity on it.
What is the equation for power?
Power=Energy/Time
How does a pendulum work?
- Before released it has gravitational potential (GP) energy but no kinetic energy. When it swings down GP energy is converted to kinetic energy.
- All energy kinetic and pendulum swings back up, converting kinetic energy to GP energy.
- All energy GP energy. Pendulum comes to a stop as it changes direction. Then swings back down and energy again transferred to kinetic energy.
Why doesn’t a pendulum keep swinging forever?
Some energy used to produce heat and pendulum stops after all energy transferred as heat.
What is momentum?
A measure of the state of motion of an object.
What two things does momentum depend on?
Mass (kg)
Velocity (m/s)
What is magnitude?
Size.
What happens to momentum during a collision or explosion?
The total momentum in a particular direction after is the same as before. Momentum is conserved, providing no external forces act.
What safety features do cars have?
Seat belts, Crumple zone, Air bags & Side impact bars.
How do seat belts work?
They lock when a car crashes, exert a force to counteract the momentum of the person.
Prevents wearer from impacting against windscreen or smashing against side of car.
Can result in bruising but injuries are a lot less severe than those is prevents.
How does a crumple zone work?
Absorbs some kinetic energy of crash.
Helps increase time over which car changes momentum which means that the force exerted on he people will be reduced.
How do air bags work?
Partially inflate on impact so are ‘squashy’.
Distribute force of impact more evenly.
Increases time taken for momentum to reduce so force exerted is reduced.
