CHAPTER 12. FORCE,MOMENTUM AND IMPULSE 12.3
See video: VPkhy at http://www.everythingscience.co.zaNewton’s First Law in action
We experience Newton’s First Law in every daylife. Let us look at the following examples:
Rockets:
A spaceship is launchedinto space. The force ofthe exploding gases pushes the rocket through the air
into space. Once it is inspace, the engines are switched off and it will keep on moving at a constant
velocity. If the astronauts want to change the direction of the spaceship they need to fire an engine.
This will then apply a force on the rocket and itwill change its direction.
EarthFigure 12.2: Newton’s First Law and rocketsSeat belts:
We wear seat belts in cars. This is to protect us when the car is involved in an accident. If acar is
travelling at 120 km·hr−^1 , the passengers in the car is also travelling at 120 km·hr−^1. When the car
suddenly stops a force is exerted on the car (making it slow down), but not on the passengers. The
passengers will carry onmoving forward at 120km·hr−^1 according to Newton I.If they are wearing
seat belts, the seat beltswill stop them by exerting a force on them andso prevent them from getting
hurt.