Motion and momentum GapFill

Imagine an object moving in a circular orbit at constant speed. Because its direction is always changing, it has a changing  speedaccelerationmotionvelocity, so it can be said to accelerate. In order for the object to accelerate, it needs to be acted on by an unbalanced or  newdifferentresultantadditional force. In circular motion, this force acts towards the  centremiddlecircumferenceedge of the circle, pulling the object into orbit. It is known as the  centre-seekingresultantunbalancedcentripetal force. In the case of a planet, this force will be the  pull of the Sungravitygravitational attractionattraction between the planet and the Sun. If a child is playing by swinging a ball on a string in a circular motion, the centripetal force is supplied by the  tensionthicknesspulltightness of the string. If this centripetal force is removed, for instance by the child letting go of the string, the ball will continue in  an elliptical orbita straight linean arca curve tangentially to the previously circular motion.

Momentum is a property of all moving objects, given by the equation momentum =  mass ÷ accelerationmass ÷ velocitymass × velocitymass × acceleration. Momentum is conserved in all interactions. The force exerted on an object is related to the momentum of an object by  force = momentum × timeforce = rate of change of momentumforce = change in momentum × timeforce = total change of momentum.

Forces are very important when discussing vehicle safety. The distance that a vehicle travels before coming to a stop is called its stopping distance, which is equal to  thinking distance – braking distancebraking distance × thinking distancethinking distance + braking distancebraking distance – thinking distance. Thinking distance is the distance travelled by a vehicle before the driver reacts to a hazard or other signal. Braking distance is the distance travelled by a vehicle while its brakes are applied, before it comes to a complete stop. Thinking distance and reaction time can be affected by factors such as  road quality, car size or alcoholroad or brake qualityage, alcohol or road qualitydistractions, alcohol or tiredness. Braking distance can be affected by factors such as  distractions, alcohol, tiredness or car speedage, alcohol or road qualitythe weather, car speed, or quality of brakes and tyresroad quality, car size or alcohol.