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Chap. 5 Motion
Chapter 5 Vocabulary
Question | Answer |
---|---|
Motion | An object's change in position over time in relation to a reference point. |
Most common reference point | Earth |
Speed | Distance traveled by an object divided by how long it took to travel that distance |
Speed Formula | S(speed)=d(distance)/t(time) |
SI Units for Speed | m/s, km/hr , ft/s |
Velocity | Speed in a given direction |
Combining Velocities | Same direction: add to find resultant velocity Different direction: subtract to find resultant velocity |
Acceleration | Rate of change in velocity over time |
Acceleration Formula | Acceleration=Final Velocity-Initial Velocity/Time |
Centripetal Acceleration | Acceleration that occurs in a circle. Constantly accelerating because it is always changing direction. |
Force | A push or pull |
Unit used to express force | Newton(N) |
Net Force | Combination of all forces acting on an object |
Balanced force | Net force = zero. No movement |
Unbalanced force | Net force does not = zero. Produces a change in motion |
Friction | Force that opposes motion between to surfaces that are in contact |
Effect of force on friction | Friction depends on how much force is pushing the two surfaces together. Changing the weight will increase friction. Changing surface area will not. |
Kinetic friction | Friction between moving objects |
Static friction | Friction that keeps objects from moving when a balanced force is applied |
Lubricants | Substances that reduce friction between two surfaces (ex. wax, oil, grease) |
Gravity | Attractive force between two objects because of their masses |
Law of universal gravitation | Created by Sir Issac Newton. States that all objects in the universe attract each other through gravitational force. The size of the force depends on the objects' masses and how far apart they are. |
Weight | How much gravity is pulling on an object. Can change due to its location. |