PhysicsForces and Motion

Ms. GoldamerCopy everything in red onto your class notes.

Section 1 SummaryA reference point is an object that appears to

stay in place.

The Earths surface is a common reference point for determining motion.

Section 1 SummarySpeed 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/s2. 5km/h360 km/hr

Summary section 1 continuedVelocity 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 ProblemsOn 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 2A 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 AnswerUnbalanced, because the ball changes speed

and/or direction.