# Physics P3 Forces and Motion

Created by AP.

HideShow resource information
• Created by: A.P
• Created on: 19-01-13 17:11
• Forces and Motion
• Forces, Mass and Acceleration
• If the forces acting on an object are balanced, it's at rest or has a constant speed. If the forces acting on an object are unbalanced, it speeds up or slows down.
• The unit of force in the newton (N).
• force = mass x acceleration
• Where F = unbalanced force in N, m = mass in kg and a = acceleration in m/s2
• The equation f=ma is used to find mass or acceleration if the resultant force is known.
• Car Safety
• Reaction time, and therefore thinking distance, may increase if a driver is...
• ...tired, under the influence of alcohol or other drugs, travelling faster or distracted (lacking concentration).
• Braking distance may increase if...
• ...thre road conditions are poor, e.g. icy, the car has not been properly maintained, e.g. worn brakes, or the speed is increased.
• For safe driving, it is important to be able to stop safely.
• Keep an appropriate distance from the car in front.
• Have different speed limits fro different types of road and locations.
• Slow down when road conditions are poor.
• Factors affecting breaking distance are:
• The greater the mass of a vehicle the greater its braking distance.
• The greater the speed of a vehicle the greater its braking distance.
• When the brakes are applied the brake pads are pushed against the disc. This creates a large friction force that slows the car down. Worn brakes reduce the friction force, increasing the braking distance.
• Worn tyres with very little tread reduce the grip of the wheels on a slippery road, leading to skidding and an increase in distance.
• Increased braking force reduces the stopping distances.
• Thinking distance increases linearly with speed.
• Braking distance increases as a squared relationship, e.g. the braking distance at 60mph is nine times the braking distance at 20mph.
• Untitled