PhySci 5.1

Measuring Motion

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Chapter 5
Lesson 1

What is a Reference Point?

When you see something moving, you are observing it compared to things around it.

Sometimes, these surrounding objects are not moving. An object that appears to stay still is called a reference point.

You can use standard directions such as north, south, east, west, right, and left to describe the object's motion. But you can also use landmarks on Earth's surface, like buildings or trees, as reference points.

Multiple Choice

When you see something moving, you are _______ it compared to things around it

• ignoring

• looking

• watching

• observing

Multiple Choice

An object that appears to stay still is called ?

• object

• reference point

• origin

• start line

What is Motion?

Motion is happening all around us, even if we can’t always see it. For example, the wind blowing throughout the earth or the cars going from place to place.

When you observe something moving, you are noticing how it changes compared to other things nearby.

Sometimes, the objects around it may be still, or not moving. When an object changes its position over time in relation to this reference point, we say that the object is in motion.

Multiple Choice

Motion is happening all around us, even if we can’t always see it.

• True

• False

What is Speed?

Speed is how fast something moves. It is calculated by dividing the distance traveled by the time it takes to travel that distance.



Most of the time, objects do not move at a steady speed. For example, during a race, you might start off slowly and then run quickly at the end to reach the finish line.

Units for speed include meters per second (m/s), kilometers per hour (km/h), feet per second (ft/s), and miles per hour (mi/h).

Multiple Select

Speed is calculated by the ____ and ____ traveled.

• distance

• time

• velocity

• measure

Multiple Choice

Which of these is NOT a measurement of speed?

• lo/l

• ft/s

• m/s

• km/h

What is Velocity?

Velocity is the speed of an object along with the direction it is moving.

An object has constant velocity when both its speed and direction do not change.

Velocity changes in the following situations:

• When the speed of the object changes

• When the direction of the object changes

• When both speed and direction change

Multiple Choice

What is velocity?

• speed and acceleration of an object

• direction of an object

• speed of an object

• speed and direction of an object

What is Acceleration?

Acceleration tells us how fast an object's speed or direction is changing. If an object speeds up, slows down, or changes direction, it is accelerating.

The units for measuring acceleration come from the units used for speed (velocity) divided by the units for time. This usually gives us a measurement in meters per second per second, which can also be written as m/s/s or m/s^2.

When an object speeds up, we call it positive acceleration. If it slows down, we refer to it as negative acceleration or deceleration.

Multiple Choice

The units for measuring acceleration comes from.. ?

• speed

• velocity

• deceleration

• motion