1. Centripetal Force

3.  An accelerating object can be undergoing a change in direction without the speed of the object changing.  That a centripetal force is a force acting towards the centre of a circle.

4.  Key: state that a force required for an object to move in a circle is a centripetal force  Stretch: draw a diagram showing the force necessary to make an object undergo circular motion  Challenge: Identify the forces that provide the centripetal force on an object in an given situation

5.  That the size of a centripetal force depends on the radius of the circular path, the speed of rotation and the mass of an object?  Is this true or false?

6.  Centripetal force  Centri = Centre  It is a force that makes a body follow a curved path, and towards the centre.

7.  Watch this.....  Now draw a force diagram explaining the forces that are acting on the person.  Does the distance from the centre of the rotating disc have an effect on the size of the forces?

8. For a moving object at a constant speed  its velocity is directed along a tangent to the circle of direction  the velocity constantly changes direction as it moves around the circle  the change of velocity is towards the centre of the circle

9.  Therefore, the object is constantly accelerating towards the centre of the circle.  So the force on the object act towards the centre of the circle.  This force that acts towards is a resultant force, called the centripetal force, because it always acts towards the centre of the circle.

10.  The mass of the body increases  The speed of the body increases  The radius of the circle increases  The direction of the centripetal forces is always towards the centre of the circle.  IF you remove the centripetal force then it will go off at an tangent.

11.  In each of these situations a single force acts as the centripetal force. Match each situation to the words:  Electrostatic force, friction, gravity, pull (tension)  1. A car travelling around a bend.  2. A stone being whirled round on the end of a string.  3. A planet moving round the sun.  4. An electron orbiting the nucleus of an atom.

12.  1. A car travelling round a bend = FRICTION  2. A stone being whirled round on the end of the string = PULL  3. A planet moving around the sun = GRAVITY  4. An electron orbiting the nucleus of an atom = ELECTROSTATIC FORCES

13.  The centripetal force of an aircraft is the resultant force of the two other forces acting on the aircraft: the weight of the aircraft and the lift of the aircraft