mechanics

• If the question says initially t=0

  if t=0 velocity=0
• Velocity time graph

  gradient is acceleration

  Total area under graph is the distance travelled

  Rest,velocity=0

  Constant velocity=straight line
• Acceleration= velocity/time
• Average speed=total distance/total time
• Maximum velocity is when acceleration=0
• If ball is dropped acceleration is positive

  If ball upwards acceleration is negative
• First law An object continues to move with constant velocity or remains at rest unless acted upon by a force
• Second law F=ma
• If suspended top and bottom forces are equal

  If i equilibrium top and bottom =0

  Forces can be in vector form -6 would mean 6 to the left and 7 up

  7
• Constant speed means acceleration=0

  Weight=gravity x mass
• s=displacement Differentiate to go down

  v=velocity Integrate to go up

  a=acceleration
• If the velocity is -6.95 the speed would be 6.95 as speed can't be negative
• Newton's third law

  If object A exerts a force on object B,then object B exerts a force on A,with the same magnitude but opposite direction
• Whenever an object is in contact with a surface,the surface exerts a normal reaction force.
• Acceleration of a person is the same as the lift
• If the lift is moving upwards take the positive direction to be upwards

  (R-mg)
• If the lift is moving downwards it makes sense for the positive direction to be down

  (mg-R)
• When 2 objects are in contact and are moving together at the same acceleration,you can consider them one object
• When there is a pulley look at the 2 particles separately
• displacement is where it starts to where it ends

  distance is all the stops it makes along the way
• average velocity=final displacement-initial displacement (initial is usually 0)
• to go from kmh-2 to ms-2

  have to square the seconds only when converting