Work and Energy Flashcards
If an object has energy then…
It has the ability to do work
What is the unit for energy?
The Joule ( J )
What is the work done a measure of?
The energy transferred
When does the work equal the total energy transferred?
If no energy is lost as heat to the surroundings (by air resistance or friction)
What is GPE?
The energy an object has due to its height above the ground.
What is KE?
The energy an object has due to its motion.
What is Hooke’s Law?
For a material or a spring the extension is directly proportional to the force provided the limit of proportionality is not exceeded.
What shows the work done to stretch or compress the string?
The area below the graph?
Where must force be plotted?
The y axis
Where must extension be plotted?
The x axis
How does a streamlined car help?
- It reduces drag
- Reduces air resistance and allows for greater speed.
- Less work needs to be done by the engine, allowing for better fuel economy
How does a lighter body and engine material help?
Reduces inertia
Acceleration rates are greater and less fuel will be used.
How does correctly inflated tires help?
Reduces rolling resistance and doesn’t heat up as much
How does a reduced engine idling loss help?
Saves fuel
A lot of KE is transferred into EPE and the greater the distance/shape change…
The smaller the average force acting.
How are airbags a safety feature?
It is designed to deflate as the person hits it with their head. The KE of the head is transferred to other forms of energy with a reduced decelerating force.
How are seatbelts a safety feature?
Prevents the occupants being ‘thrown forward’. It is also designed to stretch so the person being restrained decelerates over a longer distance and period of time.
The greater the distance…
The smaller the average force acting during the collision.
How are crumple zones a safety feature?
Certain parts of the car are designed to easily change shape during a collision. In effect, these zones absorb a lot of the car’s KE and changes it to EPE, reducing the average force during the collision.
What does a longer time of collision mean?
A reduced decelerating force.
