| A | B |
|---|
| (usually) unwanted side effect of friction | heat |
| 2 ways to reduce friction | lubrication, use wheels |
| common lubricants | oil, greese |
| friction between lubricated surfaces | fluid friction |
| a change in velocity | acceleration |
| 3 examples of acceleration | speed up, slow down, change direction |
| speed and direction | velocity |
| the usual path of a moving object | straight line |
| curved or circular motion | centripetal acceleration |
| force that causes an object to move in a curved or circular path | centripetal force |
| a line or plane that touches a curve | tangent |
| when centripetal force releases an object it moves.... | at a 90o angle in the direction of the motion |
| what caused friction | microwelds |
| friction between objects that are moving past each other | sliding friction |
| friction between objects on wheels and a surface | rolling friction |
| friction that is so strong, the object does not move | static friction |
| micro-welds are stronger than the push or pull | static friction |
| very few micro-welds because there is very little contact between the object and the surface | rolling friction |
| the micro-welds are breaking and reforming | sliding friction |
| effect of surface texture on friction | rough surface caused more friction |
| effect of weight on friction | more weight, more friction |
| force that acts on all objects moving/falling through the air | air resistance |
| 3 things that determine air resistance on an object | shape, size, speed |
| thing that does not determine air resistance | mass |
| anything shot or thrown through the air | projectile |
| curved path of a projectile | projectile motion |
| two velocities of a projectile | forward, downward |
| force diagram of a projectile | ----> <-- v |
| which will hit the ground first (object dropped from same height, object projected straight forward | both will land at the same time |
| which will hit the ground first ball 10 lbs OR ball 5 lbs (dropped from the same height) | both will land at the same time |
| why do objects dropped from the same height land at the same time (the same size & shape, regardless of mass) | gravity pulls on all objects with equal force |
| rate of acceleration due to gravity | 9.8 m/s2 |
| micro-welds are reduced because a layer of fluid separates the surfaces | fluid friction |
| centripetal force that holds a satellite in orbit around the earth | gravity |
| centripetal force that helps a car round a curve | friction between road and tire |
| centripetal force that held the ball in our experiment | tension of the string |
