Energy and motion II Flashcards
What is work done?
When a force moves an object through a distance and energy is transferred (kinetic energy transferred = work done)
What is gravitational potential energy due to?
A change in height
What is kinetic energy?
The energy of movement
What happens when an object falls?
Its gravitational potential energy is converted into kinetic energy, some of which is then turned into heat and sound energy
What happens to work done when you stretch an object?
It is stored as elastic potential energy
What happens when the force stretching an object is removed?
The elastic potential energy is converted to kinetic energy and the object returns to normal
The extension of an elastic object has what relationship with the force?
Directly proportional
What is a spring constant?
A value that depends on the material you stretch, which is representative of how stiff the spring is
What happens when too much force is applied to a spring?
The spring reaches the limit of proportionality. After this, the spring extension and force aren’t proportional, and the material will be permanently stretched
What is power?
Power is the rate of doing work (how quickly you get something done)
What is one watt?
One joule of energy transferred per second
What is momentum?
A property of moving objects
How does an object have a greater momentum?
By having a greater mass and a greater velocity
What properties does momentum have?
Size and direction
What is the relationship between momentum before and after an event?
Momentum remains the same before and after an event
What changes momentum?
Forces that act on an object
How do brakes work?
By working against the kinetic energy of the car, transferring it into heat & sound
How do regenerative brakes work?
Regenerative brakes put the wheel’s motor into reverse so the wheels are slowed, and the motor turns kinetic energy into electrical energy that is stored as chemical energy in a battery to reuse
What is safe conversion of kinetic energy and how does it help passengers in cars?
Increasing the time over which momentum changes happen which lessens the force on the passengers
What are the main methods of conversion of kinetic energy?
Crumple zones- kinetic energy is converted as it changes shape, increasing impact time
Side impact bars- help direct kinetic energy away from passengers
Seatbelts- stretch slightly, increasing time taken for wearer to stop
Airbags- stop you hitting hard surfaces
