Chapter - 3

Pages Covered - 3

• It takes an enormous force to lift a giant space shuttle off its launch pad, and to propel it into space. The booster rockets that supply the initial thrust provide a force of several million newtons. As the spacecraft accelerates upwards, the crew experience the sensation of being pressed firmly back into their seats.

• Unbalanced forces change motion

  • Forces – pushes and pulls – affect objects as they move.

  • The unit used for measuring forces is the newton (N). You lift an apple.

  •  The force needed to lift an apple is roughly one newton (1 N).

  • You jump up in the air. Your leg muscles provide the force needed to do this, about 1000 N.

• Important Forces

  • Forces appear when two objects interact with each other.

  • Each force is represented by an arrow to show its direction. Usually, the longer the arrow, the bigger the force is. Notice the convention that the arrow usually points away from the object of interest.

  • Contact Force - It's the force that reacts to the force you give, for example if you jump and land there is a opposite contact force given

  • Friction - Friction is the opposite force given to a force you give, for example if you give a force to move a box there will be friction acting on it

  • Air resistance - Air resistance is the force given by the air to oppose gravity, for example when you open your parachute and start landing, they force slows down as there is air resistance acting on your free fall

  • Up thrust - Up thrust is the force that is given opposite to the force you give these can only happen in water, for example if you jump on water you will float as there is upthrust give to the force you put on jumping