Chapter 2 Flashcards
(25 cards)
What is work done?
When a force moves an object through a distance and energy is transferred
Energy can be transferred only usefully. True or False?
False-energy can also be transferred wastefully
What are the units for work done and energy transferred?
Joules
What is gravitational potential energy?
The energy an object has because of its vertical position in a gravitational field
What happens when an object is raised vertically?
Work is done against the force of gravity and gravitational potential energy is gained
What has kinetic energy?
Anything moving
How is a car slowed down?
Kinetic energy needs to be converted into other types of energy-meaning work is done
What do falling objects do?
Convert gravitational potential energy into kinetic energy.
Kinetic energy gained = Gravitational potential energy lost
What happens to the energy when work is done to an elastic object?
It is stored as elastic potential energy
What is the definition of an elastic object?
Anything that can return to its original shape after a force has been removed.
What happens when the force is removed off an elastic object?
The elastic potential energy is converted into kinetic energy
Extension is indirectly proportional to force. True or false?
False-extension is directly proportional to force.
What is the limit of proportionality?
There is a maximum force that the elastic object can take and still extend proportionally.
What is power?
The rate of work doing or energy transferred per second
What is the unit of power?
Watts or Joules per second
Momentum has size and direction so is a vector quantity. True or False?
True
What is momentum dependent on?
Mass and velocity
What is the conservation of momentum?
Momentum before = Momentum after
When catching a ball, you bring the ball into your body, this affects the rate of change in momentum and so the force. How does it do this?
- It increases the time taken for the momentum to change,
- this decreases the rate of change in momentum
- which decreases the size of the impact force.
What do regenerative breaks do?
They put the motor in reverse slowing the wheels down. They also convert the kinetic energy into electrical energy that is stored as chemical energy in the vehicles battery.
What happens in a crash?
Kinetic energy is converted into other forms of energy in a short period of time. There is also a big change in momentum over a short space of time, meaning people experience huge forces
What do crumple zones do?
They convert kinetic energy into other forms of energy as they change shape. They also increase the impact time, decreasing the force produced by the change in momentum.
What do side impact bars do?
They direct the kinetic energy away from passengers to other areas of the car
What do seat belts do?
They stretch, increasing the time taken for the passenger to stop. This reduces the forces acting on the chest and absorbs some of the kinetic energy
