Laws of motion - weight and mass

• What is weight and what quantities does it depend on?


  Weight is the force that acts on an object due to gravity and the objects mass, the weight depends on the objects mass, and gravitational strength given the position in the field

  WEIGHT = MASS X GRAVITY
• What is the unit used for weight?


  N (newtons)
• What is the unit used for gravitational strength?


  N/KG
• What is meant by the objects centre of mass?


  The single point where an objects weight can be considered to act through
• How many newton metres are equal to one joule?


  1N/M = 1J
• State newtons first law for a stationary object


  If the resultant force on a stationary object is zero, the object will remain stationary/at rest!
• State newtons first law for a moving object


  If the resultant force on a moving object is zero, the object will remain at constant velocity, (same speed same direction)
• What can be said about the braking forces and the driving forces when a car is travelling at terminal velocity?


  The braking forces are equal to the driving forces!
• If an object changes direction, but remains at a constant speed , is there a resultant force?


  Since their is a change in direction, their must be a change in velocity meaning their is a resultant force.
• What is inertia?


  The tendency of an object to continue in its state of rest or uniform motion!
• State the defining equation for Newtons second law


  RESULTANT FORCE = MASS X ACCELERATION

  (F) (M) (A)
• State Newtons second law in words


  An objects acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass!
• What is intertial mass?

  -a measure of how difficult it is to change a given objects velocity, the ratio of force over acceleration
• State Newtons third law


  Whenever two objects interact, the forces that they exert one each other are always equal and opposite!
• What is the stopping distance of a vehicle equal to?


  the sum of the thinking distance and braking distance!
• Define distance


  How far an object moves - not involving direction - distance is a scalar quantity!
• Define Displacement 


  includes both the distance and the direction an object moves - measured in a straight line from the start point to the end point and the direction of the straight line - displacement is a vector quantity!
• Define velocity


  The speed of something IN A GIVEN DIRECTION
• Are objects that are travelling in a circular motion accelerating?


  Yes - if an object is travelling in a circular motion it is changing direction - therefore velocity (which is a vector dependant on the movement and direction) is constantly changing - a change in velocity is defined as acceleration - so although the object is not speeding up - it is still accelerating due to the change in direction!
• What is the formula for calculating speed?


  SPEED = DISTANCE / TIME
• How would you work out the average speed for non-uniform motion?


  -Calculate the total time and total distance

  -then use : AVERAGE SPEED = TOTAL DISTANCE / TOTAL TIME

  (you may have to work out time = distance/speed and sub the values into the above equation)