Physcis P2

• What is a scalar quantity?

  Quantities that have only magnitude and no direction
• What is a vector quantity?

  Quantities that have both direction and magnitude
• Velocity time graph


  Time on x axis, velocity on y axis

  Gradient shows acceleration

  Steep gradient: great acceleration

  Negative gradient: object is decelerating

  Horizontal line: object is moving at constant speed
• Distance time graph


  Time on x axis, distance on y axis

  Gradient shows velocity

  Steep gradient: fast speed

  Negative gradient: object returning to starting point

  Horizontal line: object is stationary
• Newtons 1st law of motion

  If the forces on an object are balanced, the object will continue to do what it is already doing

  -if it is stationary, will remain stationary

  -if it is moving, it will continue moving at the same speed and in the same direction
• What is inertia?


  The tendency of an object to remain in a stage of rest or continue in a state of uniform motion if not acted upon by an external force
• Newtons 2nd law of motion

  If the forces on an object are unbalanced, two things about the object can change:

  -the speed of the object may increase or decrease

  -the direction of motion may change
• Newtons 3rd law of motion

  If object A exerts a force on object B, then object B will exert an equal but opposite force on object A

  3rd law pairs must:

  -act on two different bodies

  -are always of the same type of force

  -are equal in magnitude

  -are opposite in direction
• What is terminal velocity?

  The constant speed a falling object reaches once the drag force balances the weight force
• Explain a terminal velocity graph

  -at first air resistance is small and the person accelerates as they begin to fall

  -as the person speeds up, air resistance increases

  -after a while the air resistance balances the weight. The person travels at a constant terminal velocity.

  -when the parachute is opened, there is a large upward force which causes the person to decelerate as it increases air resistance

  -The skydiver continues to slow down until the new air resistance force and weight are equal again so a new terminal velocity is reached
• What is conservation of momentum?

  If two objects collide or interact the forces acting on each one will be the same size but in opposite directions. This means that the momentum lost by one of the objects will be gained by the other object, therefore when two objects collide or interact, momentum is conserved
• Explain the energy of a ball when it is thrown into the air

  -as the ball moves upwards, the ball slows down and loses kinetic energy but gains gravitational potential energy

  -The ball stops in mid air, maximum height and gravitational potential energy, zero kinetic energy

  -has the ball moves downwards, it speeds up and gains kinetic energy whilst losing gravitational potential energy
• What is Hook’s law?

  For any object the force applied on it is directionally proportionate to the extension produced