Circular Motion Flashcards
What is circular motion?
It involves an object that moves, or travels, in a circular path.
Name four situations that are a circular motion?
Swinging a ball on a string in a circle above your head.
Roller coasters doing loop-de-loops.
Buckets full of water you swing around.
A car turning a corner.
What does changing velocity mean?
Acceleration
What angle does acceleration always occur at?
Acceleration always occurs at a right angle to the object’s motion, which is why the object changes direction but not speed.
What is centripetal acceleration?
Acceleration towards the centre of a circle.
What is centripetal force?
A force that acts toward the centre of a circular path.
What forces provide centripetal force?
Gravity, reaction, friction and tension.
What happens if the centripetal force stops acting on the object?
It won’t be in circular motion anymore, the object flies off in the direction of its velocity at that point, i.e. tangent to the circle.
Explain how a car travelling around the roundabout can be travelling at a constant speed but still accelerates.
The car’s speed is constant but its velocity isn’t as its direction is changing. This means the car is experiencing acceleration towards the centre of the roundabout (at a right angle to the velocity of the car).
Which force acting on a car travelling around the roundabout provides the centripetal force?
The friction force acting on the car’s wheels provides the centripetal force.
What would a passenger in the car experience as the car travels around the roundabout.
As the car accelerates towards the centre of the roundabout, a passenger may feel like they are being pushed towards the outside of the corner. However, this is just their body wanting to continue on its current velocity and is not a real force. The force is instead the car keeping them going around the corner.
James is practising hammer throwing with a weight attached to a wire. He spins it around above his head in a circle. Which force provides the centripetal force on the weight?
The tension force in the wire.
James is practising hammer throwing with a weight attached to a wire. He spins it around above his head in a circle. When should he let go of the weight in order to throw it forward? What will happen to the weight when he lets go of it?
It will move in a straight line in the direction of its velocity at the time of release (tangential
to the circle). He should release the weight at the point the velocity is in the desired direction.
Kerry’s car drives at a constant speed around a corner. Explain how Kerry’s car can drive at a constant speed while her velocity is still changing.
Kerry’s speed is constant but her velocity is changing because it is a vector quantity, meaning
it has direction and magnitude. The magnitude of the vector stays the same, but the direction is changing due to a centripetal acceleration towards the centre of the circular path. The
acceleration is provided by a net centripetal force which is provided by the friction force on
the tires of the car.
Maia swings a ball on a string in a circle above her head. What provides the centripetal force and how does it affect the velocity of the ball?
The centripetal force is provided by the tension force in the string. It causes an acceleration
towards the centre of the circle which changes the direction but not the magnitude of the ball’s velocity, meaning it travels in a circular path at a constant speed. The direction of the velocity is always tangential to the circle, so when Maia lets it go, it will continue in that direction.
