Which one of the following statements about circular motion is correct?

1.   ?    The speed is changing all the time.
2.   ?    The linear speed is constant but the acceleration is changing all the time.
3.   ?    The linear speed is constant and the velocity is constant.
4.   ?    The linear speed is constant but there is acceleration because the velocity is changing all the time, since there is a constant change in direction.

Which one is correct about the centripetal force?

1.   ?    It is inversely proportional to the velocity.
2.   ?    It always acts at 90 degrees to the velocity, and away from the centre of the circle
3.   ?    It always acts at 90 degrees to the velocity, and towards the centre of the circle
4.   ?    It is balanced by the centrifugal force

A model aeroplane is tethered to a post and held by a fine line. It flies in a horizontal circle. Then the line breaks. What direction will it fly in?

1.   ?    Directly to the centre of the circle.
2.   ?    Directly away from the centre of the circle.
3.   ?    In a circular path, as before
4.   ?    In a straight line at a tangent.

A satellite is in orbit. This is because:

1.   ?    There is no gravity.
2.   ?    The satellite is being held there by centrifugal force.
3.   ?    Gravity is acting as a centripetal force.
4.   ?    It is being attracted by the gravity of other objects in space.

Centripetal force can be worked out with the relationship

1.   ?    F = v^2/r
2.   ?    F = mv^2/2
3.   ?    F = mv^2/r
4.   ?    F = mr^2/v

Which one of the following statements is correct when a mass is made to move in a vertical circle

1.   ?    The tension in the string is greatest at the bottom of the circle and least when at the top.
2.   ?    The tension in the string is greatest at the top of the circle and least when at the bottom.
3.   ?    The tension is provided by a combination of centrifugal force and weight.
4.   ?    The weight acts in a direction away from the centre of the circle.

Angular velocity is measured in:

1.   ?    Metres per second
2.   ?    Degrees per second
3.   ?    No units at all
4.   ?    Radians per second

Angular velocity is used in preference to speed because:

1.   ?    The speed depends on the radius.
2.   ?    The centripetal force acts at 90 degrees to the speed.
3.   ?    The speed does not change.
4.   ?    Speed is harder to measure.

A car goes around a bend. What provides the centripetal force?

1.   ?    Gravity
2.   ?    Friction
3.   ?    Electrostatic attraction
4.   ?    No force at all.

A girl of mass 30 kg is on a roundabout of radius 5 m that makes one complete turn every 5 seconds. What is the centripetal force acting on her?

1.   ?    38 N
2.   ?    47 N
3.   ?    236 N
4.   ?    300 N