1. Study Guide

2. To describe motion accurately and completely, a frame of reference is necessary. A good frame of reference is a system of objects that are not moving with respect to each other. What frame of reference would you choose when trying to figure out how fast the butterfly is moving?

3. Distance is the length of the path between two points…measured in meters. Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point. For example, giving directions uses displacement = Walk 5 blocks north

4. Vectors are any quantity that has magnitude and direction. Displacement is an example of a vector.

5. Speed = Distance / Time and is measured in meters/second There are two ways to express speed: 1)Average speed = calculated for the entire duration of a trip. (Total distance / total time) 2) Instantaneous speed = is measured at one particular instant of a trip

6. Velocity = a description of both speed AND direction of motion. Velocity is a vector. Two or more velocities can be added together: Velocity of boat = 12 km / h PLUS the velocity of the river = 5 km/h Total velocity = 17 km/h

7. Acceleration = the rate at which velocity changes. It can be described as changes in speed, changes in direction, or changes in both. Acceleration is a vector. Acceleration results from increases or decreases in speed. Negative acceleration is also called deceleration ( an acceleration that slows an object’s speed).

8. Free Fall = acceleration of an object due to change in speed as it moves toward Earth solely because of gravity (9.8 m/s). Constant Acceleration = a steady change in velocity

9. Calculating Acceleration: Acceleration = Change in velocity / total time (v f – v i ) / t Instantaneous Acceleration = how fast a velocity is changing at a specific instant.

10. Force = a push or pull that acts on an object. It can cause a resting object to move, or it can accelerate a moving object by changing the object’s speed of direction. Force is measured in Newtons (N) Net Force = the overall force after all forces are combined.

11. Balanced Forces = when the forces on an object are balanced, the net force is zero and there is no change in the object’s motion. Unbalanced Forces = cause an object to accelerate

12. Friction = a force that opposes the motion of objects that touch as they move past each other. There are 4 types of friction. 1) Static friction = the force that acts on objects that are not moving. It always acts in the direction opposite to the applied force.

13. 2) Sliding Friction = a force that opposes the direction of motion of an object as it slides over a surface. 3) Rolling Friction = the friction force that acts on rolling objects.

14. 4) Fluid friction = a force that opposes the motion of objects through a fluid. Air resistance = fluid friction acting on an object moving through the air

15. Gravity = an attractive force that acts between any two masses. Earth’s gravity acts downwards toward the center of the planet. Gravity causes objects to accelerate downwards, air resistance acts in the direction opposite to the motion and reduces acceleration.

16. Terminal velocity = the constant velocity of a falling object when the force of air resistance equals the force of gravity.

17. Projectile motion = the motion of a falling object after it is given an initial forward velocity. Air resistance and gravity are the only forces acting on a projectile.

18. Newton’s Laws of Motion First Law of Motion = the state of motion of an object does not change as long as the net force acting on the object is zero…..INERTIA (the tendency of an object to resist a change in its motion)

19. Newton’s Second Law = the acceleration of an object is equal to the net force acting on it divided by the object’s mass. A = F / m OR F = ma

20. Mass versus Weight Mass = a measure of the inertia of an object. Does not change. Weight = a measure of the force of gravity acting on an object. Can change depending on location. Weight = Mass X Acceleration due to gravity

21. Newton’s Third Law = when one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. Momentum = the product of an object’s mass and its velocity. An object has a large momentum if the product of its mass and velocity is large.

22. Universal Forces exist throughout the universe. There are 4 of them: 1) Electromagnetic Forces = associated with charged particles. The only forces that can both attract and repel. Examples = static electricity in the dryer and magnets.

23. Strong and Weak Nuclear Forces: Strong Nuclear Force = a powerful force of attraction; acts only on the neutrons and protons in the nucleus of an atom. Weak Nuclear Force = also a force of attraction, but much weaker than the strong force. Acts over much shorter distances.

24. Gravitational Force = the weakest universal force. An attractive force that acts between any two masses. Newton’s law of universal gravitation states that every object in the universe attracts every other object. The greater the mass of any two objects the greater the gravitational force. Most effective force over long distances.