Kinetic energy of objects speeding up or slowing down Flashcards
When is work done?
when a force causes an object to move a distance
additional guidance:
‘W’ is the work done in joules, J
F is the force applied in newtons, N
d is the distance moved in the direction of the force in metres, m
What happens when work is done?
energy is transferred
What kinetic energy transfer occurs when a meteorite burns up in the atmosphere?
as a meteor enters the atmosphere, the air would create friction
the friction transfers the kinetic energy of the meteor into heat energy
What is power?
work done or energy transferred in a given time
measured in watts, W
What is gravitational potential energy?
the energy that an object has by virtue of its position in a gravitational field
What is momentum?
a property of moving objects
additional guidance:
p is momentum in kilograms metres per second, kg m/s
m is the mass in kilograms, kg
v is the velocity in metres per second, m/s
What is conservation of momentum?
In a closed system the total momentum before an event is equal to the total momentum after the event
momentum before = momentum after
Why do we need safety features in cars
if a car comes to a sudden stop, passenger will continue until another force stops them
if the passenger collides with the windscreen/dashboard/steering wheel it can cause a lot of damage
How are steering wheels and air bag an effective safety feature in cars?
seat belt helps keep passengers in their seat
stretches, increases impact time and reduces the force of collision
air bag gives the person greater time decelerate, the impact time increases so the force decreases
the air bag spreads the forces on the body across a large area
What is the crumple zone designed to do?
designed to absorb energy from the collision in order to reduce the force on the passengers
folding during a collision increases the impact time
time to come to a halt is increased so the force is decreased
What are some alternative braking systems and how are the useful?
anti-lock braking system helps stop skidding and help keeps the car under control
regenerative braking system causes a generator to charge the car’s battery when braking, prevents the heat created when braking is not wasted
