Push- A force.
Friction- A force that opposes motion.
Normal reaction force - The force that acts in an upwards direction.
Gravitational force/weight- The pull of the earth.
Air resistance- A force taht opposes the movement of objects in air.
Upthrust- An upward push.
Magnetic force- used to make electric motors rotate.
Electrostatic force- To do wit the attractions and repulsions between charges.
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Vector and Scalar
Vector changes in size and direction.
For example:
Velocity.
Force.
Acceleration.
Momentum.
Scalar only changes in size.
For example:
Temperature
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Newtons's law of motion
Newton's 1st law If the forces on an object is balanced – there is no resultant force – the object will either remain at rest or carry on moving at constant speed in a straight line. If the forces on an object is unbalanced, the object will accelerate.
Newton's 2nd law
Resultant force (N) = mass (kg) x acceleration (m/s2) or F = ma
Newton's 2nd law For every action there is an equal and opposite reaction.
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Terminal velocity
Terminal velocity is when the upward force is the same as the downward force.
Example
When a skydiver jumps off the plane, she will accelerate until she reaches terminal velocity. When her parachute opens, it will cause a sudden increase in drag force. This means that there will be an unbalanced force acting upwards, causing her to decelerate. As she slows down, the drag force decreases and a new terminal velocity is reached.
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Thinking distance and Braking distance
Thinking distance= is the time takn for the driver to respond or react
This could be increased if the driver is tired, under the influence of alcohol or drugs/ or poor visability.
Braking distance= is the time takenfor the vehicle to rest after the driver hits the brakes. This could be increased if the road is slipperry or the tyres are screwed up.
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The Turning effect of forces
Moment(Nm)= Force(N) x Perpendicular distance from the pivot(m)
An object will be balanced if:
Sum of anticlockwise moments = sum of clockwise movements
Hooke's law:
load force is directly proportional to extension provided that it is within its elastic limit
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