Motion Speed Velocity Acceleration Forces Frame of Reference

Motion Speed, 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? Speed The rate of change in position Speed = distance ÷ time or = distance time

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

Answer: • Speed = distance ÷ time • Speed = 300 km ÷ 6 hours • Speed = 50 km/hr

More practice • 1. How far can a plane travel if it flies 800 km/hr for 9 hours? • 2. How long does it take a ship to go 500 km if it travels at a speed of 50 km/hr?

Answers 1. 7200 km/hr 2. 10 hours

What is Motion? Velocity Speed 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

Acceleration • Change in velocity – Can be change in speed or direction Acceleration The rate of change in velocity Positive acceleration = speeding up Negative acceleration = slowing down (decelerate)

Acceleration = Vfinal – Vinitial Time = ∆Velocity Time or

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

ANSWER: a = 26 m/s – 10 m/s 2 s a = 16 m/s 2 s a = 8 m/s/s or 8 m/s 2

What is a Force? 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 l. Balanced forces are equal in size and opposite in direction l. 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.

Determine the NET FORCE: