Science StarterHow would you describe motion?

*Do Not use the terms move, moving or movement in your answer!

Science StarterThe speed of an animal is how fast it

is moving.

A speed of 6 m/s (meters per second) means that the animal moves a distance of 6 meters every second.

How would you measure the speed of an animal?

What do you think are the fastest animals?

Motion

Introductory VideoPhysical Science: Motion

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MotionMotion: a change in position in a certain amount of time

SpeedSpeed: the rate at

which an object moves Anything that is changing its position has speed

Example: ocean currents, the moon, a car, a person walking

SpeedFormula: speed = distance

time

Constant Speed: speed that does not change This is shown a straight diagonal line

on a distance-time graph

Average Speed: dividing the total distance by the total time

Measuring MotionSample problem: At what speed did a

plane fly if it traveled 1760 meters in 8 seconds?

Step 1 – Write the formula.Speed = Distance/Time

Step 2 – Substitute given numbers and units.

Speed = 1760 meters/8 secondsStep 3 – Solve for the unknown.

Speed = 220 meters/second (m/sec)

Measuring MotionPractice Problems:

1. A car travels 240 kilometers in 3 hours. What is the speed of the car during that time?

2. The speed of a cruise ship is 50 km/hr. How far will the ship travel in 14 hours?

A car travels 240 kilometers in 3 hours. What is the speed of the car during that time?

Step 1: Speed = Distance/Time

Step 2: Speed = 240 km/3hrs

Step 3: Speed = 80 km/hr

Answer: The speed of the car is 80 km/hr.

The speed of a cruise ship is 50 km/hr. How far will the ship travel in 14 hours?Step 1: Speed = Distance/Time

Step 2: Speed = 50km/hr

Step 3: 50 km x 14 hrs = 700km/14 hrs

Answer: The ship will travel 700 km in 14 hrs.

Measuring MotionThe speed of a moving

object is not always constant.

For example, a cyclist takes a long bike ride. She begins slowly for the first two hours and picks up speed for the third hour. After three hours, she takes a break before finishing the final two hours of her ride.

Measuring MotionClearly, her speed changes many times

throughout her journey.Dividing the total distance by the total

time does not tell you her speed for every point of her journey.

Instead it gives you her average speed.

In fact, the formula you just learned for calculating speed – distance/time – always gives you the average speed.

VelocityVelocity: speed in a

given direction

Example: Suppose a runner moves eastward at 10 m/sec

His speed is 10 m/sec

His velocity is 10 m/sec east

VelocityCombining Velocities

Suppose you are rowing a boat downstream at 16 km/hr. Would it surprise you to learn that you are actually going faster than 16 km/hr? How is this possible?

Measuring MotionThe river is also moving, say at 10 km/hr.

Since you are rowing downstream, you are going in the same direction as the river. The two velocities combine. So you are moving at 26 km/hr.

*Velocities that have the same direction are added together.

Measuring MotionIf you were rowing 16 km/hr upstream, you

would be going 16 km/hr – 10 km/hr, or 6 km/hr.

* Velocities that have opposite directions are subtracted from each other.

Frame of Reference

Frame of Reference: the background or point that is assumed to be stationary and is used for comparison when motion is described

Depends on the type of movement and the position which you are observing from

Most common frame of reference: the Earth

Frame of Reference

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