# Physics P3 2.6 Circular motion.

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What happens to the velocity of an object moving in a circle at constant speed?
The velocity of an object moving in a circle at constant speed is continually changing as the object's direction is continually changing.
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What is centripetal acceleration?
It is the acceleration towards the centre of the circle of an object that is moving round the circle.
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What does the centripetal force of an object depend on?
Its mass, its speed and the radius of the circle.
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When an object moves in a circle it is continuously changing direction, so it is continuously changing velocity, in other words it is accelerating. What is this acceleration called?
Centripetal accelleration.
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What causes an object to accelerate and what is this called?
An obect only accelerates when a resultant force acts on it. This force is called the centripetal force.
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Where does the centripetal force always act towards?
The centre of the circle.
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When does the centripetal force needed to make an object perform circular motion increase?
As the mass of the object increases, as the speed of the object increases, as the radius of the circle decreases.
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A student is whistling a conker around on a piece of string, in a horizontal circle. What force provides the centripetal force?
Tension in the string.
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What will happen to the conker if the string breaks? (follow on from previous question)
The conker will fly off in a straight line at the tangent to the circle.
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Why is centripetal force not a force in its own right?
It is always provided by another force, e.g. gravitational force, electric force or tension.
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**IN QUESTIONS ON CIRCULAR MOTION YOU MAY NEED TO IDENTIFY THE FORCE THAT PROVIDES THE CENTRIPETAL FORCE**
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## Other cards in this set

### Card 2

#### Front

What is centripetal acceleration?

#### Back

It is the acceleration towards the centre of the circle of an object that is moving round the circle.

### Card 3

#### Front

What does the centripetal force of an object depend on?

### Card 4

#### Front

When an object moves in a circle it is continuously changing direction, so it is continuously changing velocity, in other words it is accelerating. What is this acceleration called?

### Card 5

#### Front

What causes an object to accelerate and what is this called?