1. Projectile Motion, Orbiting and Centripetal force

2. Projectiles move in TWO dimensions
a projectile moves in 2-dimensions, Horizontal –applied force
and Vertical- gravitational force

3. Combining the Components
Together, these 2 components produce what is called a trajectory or path. This path is parabolic in nature.

5. You must aim higher than your Target
You must aim higher than your Target. Different angles achieve different horizontal distances.

6. Centripetal Force Centripetal means center-seeking.
The centripetal force always points toward the center of the circle about which the object moves with uniform speed.
If the centripetal force applied to the object is removed, the object will move in a straight-line. When the centripetal force ceases, the object has no unbalanced forces acting upon it and thus moves in a straight line at constant speed.

7. Circular Motion
When an object moves in a circle at constant speed, we describe it as undergoing uniform circular motion.
Its speed is constant, but its velocity is not because velocity includes direction and the object’s direction is clearly changing.

8. Circular Motion
If the string breaks, the ball flies off in a straight line. It is the force of the string that causes the acceleration in this example of uniform circular motion.

9. Uniform Circular Motion
© Simon Porter 2007
Uniform Circular Motion
For orbital motion, the centripetal force is provided by gravity
Combined horizontal force and vertical force
Earth’s gravitational attraction on moon
ALL CIRCULAR MOTION REQUIRES A
CENTRIPETAL FORCE, OTHERWISE THE
BODY CONTINUES IN A STRAIGHT LINE PATH.

10. What is Weightlessness
© Simon Porter 2007
Remember both the ship and astronaut are falling towards the earth (centripetal acceleration) v
mv2/r

11. Weightlessness—falling continually
© Simon Porter 2007
Because they are both falling together, the astronaut feels no reaction force from the floor of the space craft so she feels “weightless” (you get a small feeling of this as a lift (elevator) starts to descend).
acceleration = v2/r