Speed, forces, velocity, ernergy to move, workdone Flashcards
What does a distance time graph show?
The distance an object moves in a period of time
What is velocity?
An objects speed in a given direction.
What is a change in velocity called?
Acceleration
How do you work out the change in velocity?
Final velocity-original velocity
What does a negative acceleration mean?
The object slows down
What does a velocity time graph show?
How an objects velocity changes with time
What is the resultant force of an object?
The single force that would make an object move as all the original forces acting together.
What does it mean if there is no resultant force?
Forces are balanced and an object doesnt change speed. It is stationary
In a vehicle, …… Consumption increases if drag force increase at a certain speed. A larger forward force is needed to overcome drag forces. More energy is needed from the engine to provide a larger forward force and keep going at the same speed.
Fuel
What do streamlined objects have?
Small, cross sectional areas and smooth areas. This reduces drag forces so the objects can move faster for the same forward force.
Why does a person feel heavier in a lift than normal?
Because when a lift accelerates upwards, the force from the floor pushing upwards is greater than the weight of the person in the lift.
What is total stopping distance?
Thinking distance+ breaking distance
What is reaction time?
The time taken for a driver to react to a hazard
What can increase the thinking distance?
- if the driver is tired or distracted
- if the driver has drunk alcohol or taken drugs
What can increase the braking distance?
- if the road is wet or icy
- the tyres are worn down
- the brakes are in bad condition
- the road surface
What is aquaplanning?
Water from the surface of a wet road is channelled out through the treads of a tyre. If the tyre tread is worn down, water cannot be removed, so the car slides over a layer of water on the road and cannot be controlled. This is called aquaplanning.
What is extension?
The difference between the original length and the stretched length.
When an elastic object like a rubber band or spring is stretched:
- the extension is …….. To the force applied up to a limit.
- above the limit, extension is not propertional to the force.
Propertional
What are work done and energy transfer measured in?
Joules
What is power a measure of?
How quickly work is being done and how quickly energy is being transferred.
What does the amount of gravitational potential energy depend on?
- mass
- height above ground
All moving objects have kinetic energy. What does the amount of kinetic energy depend on?
- mass
- speed
How much work is done when lifting a 250N box by 2m?
500J
What force is needed to do a 500J of work over a distance of 5m?
100N
What is the power of a machine that does 2000J of work in 5 seconds?
400W
How much GPE does a rollercoaster car of mass 1000kg lose when it drops 5m?
1000x10x5=50,000J
At the bottom of its swing, a pendulum has ….. GPE and ….. Kinetic energy?
Maximum GPE and minimum kinetic energy
A car has more kinetic energy when ….
It is driven faster
What is the kinetic energy of a 1000kg car driven at 13 m/s?
1/2 x 1000 x 13 x 13 =84,500J
What is the unit of force?
The newton (N)
What happens to a moving object if the resultant force is zero?
It keeps moving
What happens to a moving object if the resultant force is not zero?
It speeds up in the direction of the resultant force.
If you double the resultant force applied to an object, what happens to its acceleration?
It doubles
What force is needed to give an acceleration of 2 m/s(squared) to a 4kg box?
8N
What is terminal velocity?
When there is no resultant force and the object reaches a steady speed, called the terminal velocity.
What is mass a measure of?
How much stuff is in an object.
Elastic objects can store elastic potential energy when they are?
Stretched or squashed
When an elastic object is changed from its original shape: work is …….?
Done
Until a certain limit is reached, Hookes law states that: the extension of an elastic object is ……. ………. To the force applied?
Directly propertional
A spring with k= 10N/m is stretched from 0.2 to 0.5m. The force needed is?
3N
