# Measuring Motion.

## Presentation on theme: "Measuring Motion."— Presentation transcript:

Measuring Motion

Words to Know speed magnitude velocity acceleration

All types of motion can be described, measured, and even predicted.

Rate of motion can be measured and is called speed
Rate of motion can be measured and is called speed. Velocity is another measure of motion that takes into consideration both rate of motion (speed) and direction .

speed = distance/time

velocity= distance/time in a given direction

So, if speed remains constant, but direction changes, then the velocity has changed.

The motion of an object can be described by its position, direction of motion, and speed.

We commonly talk about travel in these terms
We commonly talk about travel in these terms. For example, last week I left my house (starting position), went west (direction) on highway 70 at 50 km/hr (speed). I arrived at the beach (ending position) in 40 minutes.

But we can really measure ANY motion of any object at any time by noting its position, speed, and direction.

In addition, we can measure changes in an object’s motion and position
In addition, we can measure changes in an object’s motion and position. We can measure changing rates of speed (called acceleration) and we can measure changes in direction.

Acceleration is the measure of the change in velocity.

A race car changes velocity as it goes around the track
A race car changes velocity as it goes around the track. To calculate the acceleration of a race car, divide the change in velocity by the time it takes the velocity to change. acceleration = (final velocity - original velocity) / time or a = (v2 – v1)/t

We can apply the concepts of speed and velocity to enable us to measure time intervals.

Knowing the relationships of the velocity of planets, the moon, the earth’s rotation, etc. allow us to measure our days, months, years, etc.

We could also measure time if we know the speed of a vehicle and the distance traveled. Since speed = distance/time, it follows that time = distance/speed

What is the difference between speed and velocity?
A: only speed is distance traveled over time B: only velocity is distance traveled over time C: both are distance traveled over time but velocity takes into account direction D: both are distance traveled over time but speed takes into account direction

D: not enough information in the question
A race car travels 500 km around a track in 3.5 hours. What is the speed of the car? A: 143 km/hr B: 286 km/hr C: 165 km/hr D: not enough information in the question

An airplane travels 500 km/hour toward the southwest for 1. 3 hours
An airplane travels 500 km/hour toward the southwest for 1.3 hours. How far did the plane go? A: 385 hours B: 650 km C: 650 km/hr southeast D: 385 km

Which of the following is expressed as velocity?
A: 45 km/hr B: 45 km/hr southwest C: 45 km south D: 45 hours

Which of the following is NOT a way to measure time intervals?
A: keeping track of the movement of the moon B: knowing the speed of a vehicle and how far it traveled C: determining velocity from distance and time D: using a computerized stopwatch

A race car's beginning velocity is 0 km/sec
A race car's beginning velocity is 0 km/sec. It's velocity at the end of the first lap is 0.06 km/sec. It takes 65 seconds to make the first lap. What is the race car's acceleration? A: 9.23 km/s B: 9.23 km/s/s C: 39 km/s/s D: 39 sec

A storm becomes a hurricane as it is traveling at 17mph toward the northwest. It covers 1400 miles before being downgraded to a tropical storm. How long was the hurricane active? A: 82 hours B: 8 days C: 23,800 hours D: 14 days

A train travels 2500 km in 17 hours. What is the train's average speed?
A: 425 km/hr B: 147 km/hr C: 42.5 km/hr D: none of the above

A: the car was traveling at 33 mph
As you are traveling down main street at 30 mph, a car passes you going in the same direction. What can you tell about the car that passed you A: the car was traveling at 33 mph B: the car passing you was going more than 30 mph C: the car passing you was accelerating at a rate of 5 mph/h D: nothing - there is not enough information

A: they will meet after traveling 30 minutes
A speed boat is traveling at 65 mph south. Another is traveling at 65 mph west. What can you tell about the boats? A: they will meet after traveling 30 minutes B: they have the same speed but not the same velocity C: they have the same velocity but not the same speed D: they have the same acceleration and the same velocity