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What is a scalar quantity?
Only has a size
What is a vector quantity?
Has a size and a direction
What is a relative speed?
How fast something is going relative to something else
What are four equations of motion?
- s = (u + v)/2 xt
- v = u + at
- s = ut + 0.5at2v2 = u2 + 2as
What does 'u' represent?
What does 'v' represent?
What does 's' represent?
What does 't' represent?
What does 'a' represent?
What is a projectile?
Something that is projected, or dropped, and from then on only has Earth's gravitational field strength acting on it (ignoring air resistance)
What shape is the path of a projectile?
What is the overall/resultant velocity of the ball?
The vector sum of the horizontal and vertical motion
What do projectile calculations use?
The equations of motion
When do forces occur?
When two objects interact
What are the two forces sometimes called?
An interaction pair
What are two examples of acting forces?
How does recoil involve forces?
- When a gun is fired, the bullet exerts a force on the gun equal and opposite to the force exerted by the gun on the bullet
- So, the bullet travels out of the barrel and the gun recoils in the opposite direction
- The bullet travels much faster forwards than the gun does backwards because the bullet is much lighter
How do rockets use forces?
- When gas particles collide with things they exert a force on them
- In a rocket engine particles of hot gas collide with the walls, exerting a force on the walls and the wall exerts an equal force on them
- The force from the wall pushes the gas particles out of the exhaust
- The force from the gas on the wall pushes the rocket forwards
- The force pushing the rocket upwards must be larger than the force of gravity and air resistance of it won't take off
- So, for large rockets, used to lift satellites into orbit above Earth, you need a large number of particles moving at high speed to produce enough force to lift the rocket
How can you work out momentum?
momentum = mass x velocity
What is momentum before equal to?
- Momentum after
- Momentum is conserved
What does 'm1' represent?
Mass of the first object
What does 'm2' represent?
Mass of second object
What does 'u1' represent?
Velocity of first object
What does 'u2' represent?
Velocity of second object
What does 'v' represent?
Velocity of combined objects
What does kinetic energy say about gases?
They are randomly moving particles
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