Iffat Sardharwalla March 2010 _____ ___ ____ _____ Newton’s first law of motion: An object’s speed will only change if a force is applied. Newton’s second law of motion: Speed or acceleration is proportional to the force. Newton’s third law of motion: Every action has an equal and opposite reaction. Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Forces Forces can’t be seen, but the effect of a force can be seen. They are measured in newtons – N They usually act in pairs (1st Law of motion) They always act in certain direction A newton meter is used to measure forces. Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Forces Two things make up a force 1. its size, how strong a push or pull is, and 2. its direction, which way it pushes or pulls. We draw forces as arrows. 1. The length of the arrow shows how strong the force is and 2. way it points shows the direction of the force. Iffat Sardharwalla March 2010

Balanced and Unbalanced Forces Change the Speed and or Direction of Moving Objects Balanced Forces produce NO change in Movement The forces on the person are balanced The floor pushes upward on the person Gravity pulls downwards on the person Greater Force Smaller Force Iffat Sardharwalla March 2010

Forces & Movement Forces are nearly always PUSHES and PULLS Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Forces can make objects do FIVE things 3. Change Direction Like hitting a ball with a bat Speed up Like kicking a ball 2. Slow down Like drag or air resistance 5. Change shape Like stretching, twisting, compressing and Bending 4. Turn Like turning a spanner Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Look at some of the forces in action Are they Balanced or Unbalanced? Tasks Now draw the arrows to show the Direction of the forces Strength of the forces Iffat Sardharwalla March 2010

Show the forces acting on the Owl sitting and reading Is the force acting on the Owl balanced or unbalanced? Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Think about this situations If you were pushing these elephants to move… 1. Which will need more force to move? Why? 2. Which direction would they be travelling? Why? 3. Which elephant will move faster? Why? Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting on this clock Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting? Iffat Sardharwalla March 2010

Where are the forces acting? Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting? Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting? Iffat Sardharwalla March 2010

Where are the forces acting? Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting? Look carefully at the insect and the frog Iffat Sardharwalla March 2010

Iffat Sardharwalla March 2010 Where are the forces acting? Look carefully at the motion of the ball Iffat Sardharwalla March 2010