Energy 2.1 Flashcards
(21 cards)
What do we call the force that makes objects attract each other?
Gravity
What does the size of the force of gravity depend on?
Distance between the objects. Objects closer to each other exert a bigger force of attraction.
The mass of the objects. Bigger mass = larger force of attraction
What is the Earth’s gravitational field strength?
10N/Kg
How do you calculate weight?
Weight = mass x gravitational field N = Kg x N/Kg
What is weight?
The pull of gravity acting on an object
What is mass?
The amount of matter in an object. STUFF
Where does an object’s mass change?
Nowhere. The mass of an object has the same value anywhere in the universe
Where does a man object’s weight change?
An object has a different weight on different planets.
How do you find the centre of mass of a regular object?
Mark the axes of symmetry on an object. The centre of mass is where the axes of symmetry cross.
How do you find the centre of mass of an irregular object?
1- Drill a small hole in the object and hang it up so it is free to swing.
2- Hang a plum line from the same suspension point. Mark this line
3- Drill another whole at a different location within the object.
4- Again band a plum line to determine the vertical and mark it on.
5- Where the lines cross is the centre of mass.
How do you calculate work done?
Work done = force x distance
J = N x m
What happens when work is done?
A force moves an object and energy is transferred
What is work done the same as?
Energy transferred
What is work done measured in?
Joules (J)
How do you calculate power?
Power (W) = work done (J) / time (seconds)
How do you calculate efficiency?
Efficiency = useful energy you get out / total energy
What does efficiency mean?
The more efficient a device, the less energy is wasted
What is power
Rate of energy transfer
What diagrams represent efficiency?
Sankey diagrams
When is more work done?
The force is bigger
The object moves further - its displacement is bigger
When is work done?
A force causes a displacement of the object (that is, movement along the line of action of the force)
