Section 1: Forces and Motion Flashcards
Scalar quantities
Scalars have a magnitude (size) only
e.g temp and speed
Moments definition
Moment = the turning effect of a force
Principal of moments
If the object is in equilibrium:
sum of clockwise moments = sum of anti-clockwise moments
Centre of mass
The point where the whole of the mass of the object appears to be concentrated
Vector quantities
Vectors have both magnitude and direction
e.g force and displacement
Resultant force
The sum of all forces acting
Reaction / contact force
Force created by a body as a a reaction to a force being applied
e.g a book on a table
Upthrust
Upward force on a body caused by the fluid (water or gas) being displaced around it
Gravitational force
Force due to gravitational attraction. Can act at a distance
Magnetic force
Force caused by magnetic attraction. Can act at a distance
Electrostatic force
Force caused by attraction between charges. Can act at a distance
Engine force
Forward force e.g created by a car engine
Tension
Force tending to stretch or elongate something
Lift
Upward force on a airplane
Friction
Resistant force that opposes the motion of an object
Air/water resistance / Drag
Frictional force caused by particles colliding with the body that opposes motion
Newton’s 1st law
An object will remain stationary or continue at a constant velocity, unless acted upon by a resultant force
Newton’s 2nd law
F = m x a
Force (N) = mass (kg) x acceleration (m/s2)
Newton’s 3rd law
For every action there is an equal and opposite reaction
Stopping distance
Stopping distance = Thinking + Braking distance
Factors affecting thinking distance
- age
- tiredness
- influence of alcohol/ drugs
- speed of car
What is thinking distance
Distance travelled between when the driver has seen the hazard and puts his foot on the brake
thinking distance = reaction time x speed