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Bicycle wheels rotate with a circular motion.

# Forces - Circular Motion

This GCSE Physics quiz about forces will challenge you on circular motion. The International Space Station (the ISS) is a temporary home to astronauts of many different nationalities. It orbits the Earth with a period of about one and a half hours, moving at a speed of almost 28,000 kilometres per hour. Its path across the sky is entirely predictable and it can be spotted easily crossing the night sky if you know where and when to look. Although its orbit is not entirely circular, it essentially follows the rules of circular motion.

Circular motion can be defined as a movement along a circular path. Newton's first law of motion states that a moving object will travel in a straight line at a constant velocity unless a force acts on it.

1.
What does increasing the acceleration of an object following uniform circular motion change?
Direction of motion
Speed of object
Both the direction and speed of the object
Neither speed nor direction
Acceleration is related to velocity so any answer that includes the word speed must be incorrect
2.
Which force acts as the centripetal force responsible for a car travelling around a bend?
Friction
Electrostatic force
Gravity
Tension (Pull)
If the centripetal force required to maintain the circular motion of the car is greater than the friction of the tyres against the road, the car skids. In wet conditions, friction is greatly reduced which is why you have to drive more slowly round corners when the road is wet
3.
If a driver drives around a bend faster than normal, what happens to the size of the centripetal force needed to keep the car going around the bend?
It doesn't change
It increases
It decreases
The car will crash whatever happens
Make sure that you learn the factors that affect the magnitude of a centripetal force
4.
What name is given to the resultant force that acts towards the centre of a circle?
Centrifugal
Centripetal
Centipede
Centimetre
You need to be able to identify what is responsible for the centripetal force, for example gravity for orbiting bodies
5.
If an object orbits around a point five metres away in three seconds, what will happen to the speed of the object if the object's orbit is increased to six metres?
Stays the same
Decrease
Increase
Impossible to tell
The speed will increase as the object will take the same time to complete one orbit. As the distance the object needs to travel increases, the speed must also increase to obey the laws of motion
6.
Which of the following is an example of uniform circular motion?
A ball travelling through space
An artificial satellite
Racing car
All of the above
Whilst a racing car during a race will experience circular motion, it is not uniform circular motion. Strictly speaking, only satellites in geostationary orbits are circular, however, for the GCSE, artificial satellites are regarded as following circular motion rules
7.
What can increase the centripetal force required to keep an object in uniform circular motion about a point?
The mass of the object
The speed of the object
All of the above
An increase in mass and speed or a decrease in radius increases the centripetal force
8.
If the centripetal force acting on the Moon were to suddenly stop acting, what would happen to the Moon?
It would continue to orbit unaffected
It would come crashing to Earth
It would go flying off into space
It would be swallowed by the black hole that would result
It would behave in accordance with Newton's first law and continue on a straight path through space until influenced by another force. The direction of travel would be the directional component of the velocity at the instant that the force of gravity stopped
9.
An object moving in a circle continuously accelerates towards what?
A predefined point outside of the area of the circle
A path perpendicular to the surface of the circle
The centre of the circle
None of the above
It accelerates towards the point of origin of the centripetal force
10.
Which force acts as the centripetal force responsible for the circular motion of planets orbiting the Sun?
Electrostatic force
Gravity
Tension (Pull)
Friction
Gravity is always a pulling force