MotionSpeed, Velocity,

Acceleration & Forces

Frame of Reference

Object or point from which motion is

determined

What is Motion?

Motion: A change in position of an object compared to a reference point

Motion involves all of the following:

What is motion?

• If you are standing in one place, and your friend walks by you, are you moving relative to your friend?

– Is your friend moving relative to you?

– Is either of you moving relative to the earth?

Answer:

• You are moving relative to your friend, and your friend is moving relative to you!

• You (the Joker) are not moving relative to the earth, but your friend is. You are both moving relative to the sun!

What is motion?

• If you and your friend are walking down the hall together at the same speed, in the same direction, are you moving relative to your friend?

– Is your friend moving relative to you?– Are either of you moving relative to the earth?

Answer:• You are NOT moving relative to

your friend, and your friend is NOT moving relative to you. You both are moving relative to the earth.

What is Motion?

SpeedThe rate of change in position

Speed = distance ÷ time or = distance time

Speed

Example: A car travels 300km in 6 hours. What is the speed of the car?

Answer:Answer:

•Speed = distance ÷ timeSpeed = distance ÷ time•Speed = 300km ÷ 6 Speed = 300km ÷ 6

hourshours•Speed = 50km/hrSpeed = 50km/hr

More practiceMore practice

•1. How far can a plane travel 1. How far can a plane travel if it flies 800km/hr for 9 hours?if it flies 800km/hr for 9 hours?

•2. How long does it take a ship 2. How long does it take a ship to go 500 km if it travels at a to go 500 km if it travels at a speed of 50km/hr?speed of 50km/hr?

AnswersAnswers

1.1.7200km/hr7200km/hr2.2.10 hours10 hours

What is Motion?

VelocitySpeed plus direction

Example: 50 km/hour north

Velocity

•Speed in a given direction.

•What is the velocity of a boat that travels from Lancaster to Baltimore(10 miles) in 15 minutes?

Answer

•Speed = distance ÷ time•Speed = 10 miles ÷ 15

minutes•Speed = 0.67 mi/min•Velocity = 0.67 mi/min NW

AccelerationAcceleration•Change in velocityChange in velocity

– Can be change in speed Can be change in speed oror direction direction

AccelerationThe rate of change in velocityPositive acceleration = speeding upNegative acceleration = slowing down (decelerate)

Acceleration = Vfinal – Vinitial

Time or

= ∆Velocity Time

Acceleration problemAcceleration problem• A roller A roller

coaster’s coaster’s velocity at the velocity at the top of a hill is top of a hill is 10m/s. Two 10m/s. Two seconds later it seconds later it reaches the reaches the bottom of the bottom of the hill with a hill with a velocity of velocity of 26m/s. What is 26m/s. What is the acceleration the acceleration of the roller of the roller coaster?coaster?

ANSWER:

a = 26m/s – 10m/s 2 s

a = 16m/s 2s

a = 8m/s/s or 8m/s2

FORCE = Any push or pull which causes something to move or change its speed or direction

What is a Force?

Forces can be BALANCED or UNBALANCED

Balanced forces are equal in size and opposite in direction

UNbalanced forces are not equal in size and/or opposite in direction. If the forces on an object are UNBALANCED, we say a NET force results.

What is a Force?

Determine the NET FORCE: