Section 1 Summary A reference point is an object that appears to stay in place. The Earths surface is a common reference point for determining motion.

Section 1 Summary Speed is a measure of how fast something is moving. Average Speed = total distance/total time. The speed at any instant is called “instantaneous speed”.

Answers: 1. 2 m/s 2. 5km/h 360 km/hr

Summary section 1 continued Velocity is the speed of an object in a particular motion.

Velocity can change by changing speed or direction. What’s are the 2 “resultant velocities” on page 121?

Acceleration is the rate that velocity changes over time. Average Acceleration = Final velocity-starting velocity/time.

Practice Problems On a separate piece of paper: vf=final velocity, vi = starting velocity. Find the average acceleration for A)vf = 23, vs = stopped, time=36 sec. B)vf= 85, vs = 5 m/s, time = 40 sec C) vf = 29, vs =2 m/s, time = 9 seconds D) vf = 13, vs = 3 m/s, time = 2 seconds

Section 2 A force is a push or pull exerted on an object. What does “Exerted” mean? How do I determine the “net force”?

Answer & Questions “Exerted” means to put on to. Net = add all forces acting on the object. Are the forces on a soccer ball balanced or unbalanced? How do you know?

Soccer Ball Answer Unbalanced, because the ball changes speed and/or direction.