Important terms, Unit 1
Type of forces - What is it?
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.
Vector and Scalar
Vector changes in size and direction.
Scalar only changes in size.
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.
Terminal velocity is when the upward force is the same as the downward force.
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.
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.
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
load force is directly proportional to extension provided that it is within its elastic limit