Force

Force

1. Newton's Laws

   • Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force (aka. inertia).
   • The third law states that for every action (force) in nature there is an equal and opposite reaction.
   • The second law explains how the velocity of an object changes when it is subjected to an external force.

2. Formulas

   • Speed = distance / time
   • net Force = mass x acceleration
   • Acceleration = v - u / time
   • Pressure = force / area
   • Density = mass / volume
   • Weight = mass x gravitational acceleration
   • (Hooke's Law) F = kx
   • Work Done = force x distance

3. Forces

   • SCALAR VS VECTOR
     • SCALAR quantities have magnitude only. (speed)
     • VECTOR quantities have magnitude and an associated direction. (velocity)
   • CONTACT VS NON CONTACT
     • contact forces - the objects are physically touching e.g. friction, air resistance or tention
     • non-contact - the objects are physically separated e.g. gravitational force, electrostatic force or magnetic force
   • RESULTANT FORCES
     • resultant force = the total effect of all the different forces acting on an object
   • WORK DONE AND ENERGY TRANSFER
     • work is done when a force causes an object to move. the force causes a displacement
   • GRAVITY
     • weight is the force acting on an object due to gravity
     • all matter has a gravitational field that causes attraction. the field strength is much greater for massive objects

4. Elasticity

   • SPRING CONSTANT
     • stretching - when a spring is stretched, the force pulling it exceeds the force of the spring
     • bending - when a shelf bends under the weight of too many books, the downward force is from the weight of the books, and the shelf is resisting this weight
     • compressing - when a car goes over a bump in the road, the force upwards is opposed by the springs in the car's suspension
   • ELASTIC DEFORMATION
     • Elastically deformed - stretched object that returns to it's original length after the force is removed
   • INELASTIC DEFORMATION
     • Inelastically deformed - stretched object that does not return to its original length after the force is removed

5. Stopping Distance

   • THINKING DISTANCE
     • distance travelled before the driver applies the brakes
   • BRAKING DISTANCE
     • distance a vehicle travels after the brakes have been applied

6. Displacement

   • VELOCITY
     • acceleration
   • DISTANCE
     • speed