- – An object can have one or more forces acting on it at the same time.
- – The sum of these forces is called the resultant force.
- – A resultant force is zero when all the forces are balanced.
- – If the forces aren’t balanced then the resultant force is not zero. An object will then move as dictated by the force.
- – An object accelerates only when the resultant force isn’t zero.
- – a = F / m
- – The distance it takes for a vehicle to stop depends the thinking distance and the braking distance.
- – When a vehicle is travelling at a steady speed the resultant force is zero.
- – The driving force from the engine is balanced by a number of resistive forces including air resistance.
- – When a vehicle speeds up the force of gravity and the reaction force coming from the road stay balanced and the driving force becomes greater than the resistive forces.
- – When a vehicle slows down either the resistive forces need to increase and/or the driving force coming from the engine needs to be reduced.
- – stopping distance = thinking distance + braking distance
- –
The thinking distance increases with the speed at which the vehicle is travelling. It also increases as the reaction time increases. - – The reaction time can be affected by a number of factors.
- – The braking distance is the distance it takes a vehicle to stop once the brakes have been applied.
- – The speed at which at object falls is affected by its weight and air resistance.
- – Once an object is falling at a steady speed it’s reached its terminal velocity.
- – Mass is the amount of stuff contained within an object.
- – Weight is a force which acts on the stuff.
- – W = m x g
- – If an object is falling to Earth: W = m x a
- – An elastic object is able to store energy as elastic potential energy.
- – Hooke’s Law states that the extension of an elastic object and the force applied to it are directly proportional to one another.
- – Hooke’s Law is only correct if the elastic limit, which is the limit of proportionality, is not exceeded.
The thinking distance increases with the speed at which the vehicle is travelling. It also increases as the reaction time increases.