Physics- Forces

Speed = Distance / Time Distance = Speed x Time Time = Distance / Speed SPEED - Metres per second (m/s) DISTANCE - Meters (m) TIME - Seconds (s)

A Scalar quantity only has MAGNITUDE (size) eg- distance, speed, time, mass, energy

A Vector quantity has both MAGNITUDE and DIRECTION eg- displacement, velocity, acceleration , force

Speed and Velocity can both be used to measure how quickly something is moving, in metres per second.

Distance and Displacement are both measured in metres, but show how far something has travelled in different ways. DISTANCE shows how far an object has travelled DISPLACEMENT shows how far an object is relative to it’s starting position, (to do with direction). So how far it is from where it started.

Negative Displacement- finished behind the starting line.

A negative velocity means it is travelling in the reverse direction.

Velocity = Displacement / Time Displacement = Velocity x Time Time = Displacement / Velocity

Distance - Time graphs can be used for calculating the speed of a moving object by calculating it’s gradient.

The greater the speed a speed that is changing, so straight lines mean constant speed No movement, stationary an object with a negative displacement

Pick two points on a line, a good distance apart, and do Change in y / Change in X

Acceleration is the rate at which the speed of a moving object is changing.

ACCELERATION = CHANGE IN SPEED / TIME a = (v-u) / t v= final speed u= initial speed The unit for Acceleration is m/s squared Final Speed = Initial Speed + Acceleration x Time OR v = u + at Time = (Final speed - Initial speed) / acceleration Where the time is at 0, on the y intercept.

the object is slowing down (deceleration or retardation)

A Speed - time graph can be used for calculating the acceleration of a moving object, simply by calculating it’s gradient. It can also be used for calculating the DISTANCE TRAVELLED by a moving object, simply by calculating the area under the graph. This can be done by: -Counting squares -Finding the area under the triangle (1/2 bh) -Finding the area under the rectangle (bh) -Finding the area under the trapezium -1/2(a+b)h -Or a combination of the above

the greater the acceleration the object is decelerating The object is travelling at a constant speed The object is stationary/ not moving

push or a pull

-Change Speed (Start, Speed up slow down or stop). -Squash or Stretch an Object -In contact with each other or sometimes at a distance

The unit for force is the Newton (N).

-Weight -Reaction -Upthrust or Lift -Friction or Air Resistance -Thrust or Driving force -Tension

The effect of Gravity on a mass, acting straight down.

The effect of a surface pushing on an object, at right angles to the surface.

The supporting force exerted by a fluid on an object, acting upwards.

A resistive force attempting to slow an object, (due to rubbing on a surface, or against the air), opposing the motion.