Momentum (AQA GCSE Physics: Combined Science)

• A moving object has momentum which is defined by the equation:

p = mv

• Where:
  • p = momentum in kilogram metre per second (kg m/s)
  • m = mass in kilograms (kg)
  • v = velocity in metres per second (m/s)

• This means that an object at rest (i.e v = 0) has no momentum
• Momentum keeps an object moving in the same direction, making it difficult to change the direction of an object with a large momentum

• Since velocity is a vector this means that the momentum of an object also depends on its direction of travel
• This means that momentum can be either positive or negative
  • If an object travelling to the right has positive momentum, an object travelling in the opposite direction (to the left) will have negative momentum

The tennis ball's momentum is negative when it moves in the opposite direction to which it initially was travelling in

• Therefore, the momentum of an object will change if:
  • The object accelerates (speeds up) or decelerates (slows down)
  • Changes direction
  • Its mass changes