3. What’s going on? LOs
To do
Draw a diagram showing the forces on the moving car (ignore
air resistance).
Q. Which of these forces would exist if the car was stationary?
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
4. Lesson focus
• An introduction to circular motion
Learning objectives
At the end of the lesson you will be able to:
• describe motion in a circle in terms of acceleration and force;
• use the equation for speed v = 2πr/T ;
• define the radian;
• convert angles from degrees into radians and vice versa.
Circular motion
5. Learning outcomes
All of you should be able to
• explain why an object moving in a circle is accelerating;
• describe the direction of this acceleration;
• explain why this object moves in a circle;
• describe the direction of the resultant force on the object;
• describe everyday examples of circular motion.
Some of you may be able to
• describe the origin of centrifugal forces.
Circular motion
6. Moving in circles LOs
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
7. Moving in circles LOs
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
8. Moving in circles LOs
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
9. Acceleration - recall LOs
To do
1. Define acceleration.
2. What causes acceleration?
3. In what direction does acceleration happen?
Circular motion
10. Changing direction is acceleration LOs
Imagine a car travelling at a constant speed. It moves towards the right and
then, instantaneously, turns through ninety degrees.
u
v
To do
Use vector subtraction to work out the direction of the change of
velocity.
Circular motion
11. Changing direction is acceleration LOs
To do
Now do the same thing for movement in a circle.
u
v
v - u
- u
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
12. Changing direction is acceleration LOs
To do
Repeat the exercise for a smaller movement.
u
v - u v
- u
In which direction does the force causing the acceleration act as the change
in direction becomes smaller?
Circular motion LO 1: describe motion in a circle in terms of acceleration and force
