Measuring MotionMeasuring Motion

Words to KnowWords to Knowspeedspeed

magnitudemagnitudevelocityvelocity

accelerationacceleration

All types of motion can All types of motion can be described, measured, be described, measured,

and and even predicted.even predicted.

Rate of motion can be Rate of motion can be measured and is called measured and is called

speedspeed. . VelocityVelocity is another is another measure of motion that measure of motion that takes into consideration takes into consideration

both rate of motion (speed) both rate of motion (speed) and direction .and direction .

speed = distance/timespeed = distance/time

velocity= distance/time velocity= distance/time in a given direction in a given direction

So, if speed remains So, if speed remains constant, but direction constant, but direction

changes, then the changes, then the velocity has changed.velocity has changed.

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

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 In addition, we can measure changes in an measure changes in an

object’s motion and object’s motion and position.position.

We can measure We can measure changing rates of speed changing rates of speed (called (called accelerationacceleration) and ) and we can measure changes we can measure changes

in direction.in direction.

Acceleration is the Acceleration is the measure of the measure of the

change in velocity.change in velocity.

A race car changes velocity A race car changes velocity as it goes around the track. as it goes around the track. To calculate the acceleration To calculate the acceleration

of a race car, divide the of a race car, divide the change in velocity by the change in velocity by the

time it takes the velocity to time it takes the velocity to change. change.

acceleration = (final velocity - original acceleration = (final velocity - original

velocity) / timevelocity) / time oror

a = (va = (v22 – v – v11)/t)/t

We can apply the We can apply the concepts of speed and concepts of speed and velocity to enable us to velocity to enable us to measure time intervals.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 = Since speed = distance/time, distance/time, it follows that it follows that

time = distance/speedtime = 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

directionD: both are distance traveled over time but speed takes into account

direction

A race car travels 500 km around a track in 3.5 hours. What is the

speed of the car?

A: 143 km/hrB: 286 km/hrC: 165 km/hr

D: not enough information in the question

An airplane travels 500 km/hour toward the southwest for 1.3

hours. How far did the plane go?

A: 385 hoursB: 650 km

C: 650 km/hr southeastD: 385 km

Which of the following is expressed as velocity?

A: 45 km/hrB: 45 km/hr southwest

C: 45 km southD: 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 traveledC: determining velocity from

distance and timeD: using a computerized

stopwatch

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/sB: 9.23 km/s/sC: 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 hoursB: 8 days

C: 23,800 hoursD: 14 days

A train travels 2500 km in 17 hours. What is the train's average

speed?

A: 425 km/hrB: 147 km/hrC: 42.5 km/hr

D: none of the above

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 mphB: the car passing you was going

more than 30 mphC: the car passing you was

accelerating at a rate of 5 mph/hD: nothing - there is not enough

information

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