Download What Is Motion?

What Is Motion?
Science Words
Say each word quietly to yourself. Then read the meaning.
Read the tip to help you remember.
position [puh•ZISH•uhn] the location of an object in relation to a nearby object or place
Position and place begin with the same sound. The position of something is its place
compared to other
objects.
The girl’s position is
described with reference to
the boy.
The boy’s position is
described with reference to
the girl.
The girl is in front of the boy.
The boy is behind the girl.
motion [MOH•shuhn] a change in position
Motion and move begin the same way. Something in motion moves from one place or position
to another.
speed [SPEED] how the position of an object changes during a certain amount of time
Speed and seconds begin with the same sound. Speed is how many seconds (minutes or hours)
it takes to get from one place to another.
velocity [vuh•LAHS•uh•tee] the speed of an object in a particular direction
Velocity ends with the sound at the beginning of east. Your velocity may be one meter per
second east. If you are going in the opposite direction, your velocity may be one meter per
second west.
These runners may be traveling at the same speed, but not at the same velocity.
What Is Motion?
force [FAWRS] a push or a pull. A force can change the speed or direction of an object.
Force and friction begin with the same sound. Friction is a force that slows things down.
acceleration [ak•sel•er•AY•shuhn] any change in velocity
A car ad may brag about a car’s acceleration—how fast the car can get from standing still to
highway speeds.
In science, acceleration is about any change in velocity, including how fast a car can stop.
Science Concepts
Read the Ideas more than once. Do your best to remember them.
1.
An object’s position is where the object is compared to something else.
2.
The “something else” is called a reference point.
3.
A reference point may be something in the background, or the whole background or frame of
reference.
4.
When an object changes position, it is in motion.
5.
Speed is a measure of the time it takes for an object to travel a particular distance.
6.
Velocity is how fast the object moves and in which direction it moves.
7.
“30 km/hr” describes a car’s speed; “30 km/hr, south” describes a car’s velocity.
8.
A force can change the speed or direction of something.
9.
Friction, which works against the direction of motion, slows things down.
10. Acceleration is any change in velocity—going faster, slower, or in a different direction.
What Is Motion?
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____ 1. To make sure your measurements are clear, it is important to use appropriate units. Which of these is a
unit of distance?
A.
B.
C.
D.
gram
liter
meter
second
____ 2. To make sure your measurements are clear, it is important to use appropriate units. Which of these is a
unit of time?
A.
B.
C.
D.
gram
liter
meter
minute
____ 3. Cars, bicycles, and people can all be objects in motion. What is it about an object in motion that is
constantly changing?
A.
B.
C.
D.
acceleration
position
speed
velocity
____ 4. Cars, bicycles, animals, and people are all objects that can be in motion. Which statement about motion is
correct?
A.
B.
C.
D.
An object in motion is accelerating.
Motion is the change in position of an object.
Gravity and friction are responsible for all motion.
An object in motion has no speed, but it does have velocity.
____ 5. Velocity is a measurement related to motion. What is velocity?
A.
B.
C.
D.
the rate at which acceleration changes
a force that opposes motion between two surfaces that are touching.
a measure of both the speed and direction of a moving object
the same as speed, that is, a measure of how fast something moves
____ 6. Which best describes friction?
A.
B.
C.
D.
a unit of the metric system
a unit that is a measure of force
energy in the form of pushing or pulling
a force that opposes motion between two surfaces that are touching
____ 7. Forces can affect the rate of an object’s motion. Which of these is a force?
A.
B.
C.
D.
acceleration
gravity
speed
velocity
____ 8. Jareem rode his bike. He traveled 30 km. It took him 3 hr. If Jareem rode at a constant speed, how fast
was he traveling?
A.
B.
C.
D.
3 km/hr
10 km/hr
30 km/hr
90 km/hr
____ 9. A train travels 200 km in the same direction in 2 hr. What is this train’s velocity?
A.
B.
C.
D.
2 km/hr
100 km/hr
200 km/hr
400 km/hr
____10. Kinan runs at a speed of 8 min/mi. How long would it take Kinan to run 4 mi at this rate?
A.
B.
C.
D.
2 min
8 min
32 min
64 min
____11. Ashwath walked for 3 hr at a speed of 10 km/hr. How far did Ashwath walk?
A.
B.
C.
D.
3 km
10 km
30 km
300 km
____12. An object moves from point A to point B in 2 min, at a constant rate.
What is the velocity of the object?
A.
B.
C.
D.
2 min/m
9 min/m
9 m/min
18 m/min
____13. Velocity and speed are both measurements describing an object’s motion. What is a difference between
velocity and speed?
A.
B.
C.
D.
Speed depends on acceleration, but velocity does not.
Speed does not depend on direction, but velocity does.
Speed depends on velocity, but velocity does not depend on speed.
Velocity depends only on friction, but speed depends only on gravity.
____14. Benny drops a ball off a bridge. The ball drops straight down, as shown in the diagram.
What happens to the ball as it falls?
A.
B.
C.
D.
Both its speed and acceleration stay the same.
Both its speed and acceleration increase.
Its speed decreases, but its acceleration increases.
Its speed increases, but its acceleration decreases.
____15. Aviv is riding his bicycle. He pedals hard to gain speed. Then he coasts along without pedaling. What
kind of energy does the coasting represent?
A.
B.
C.
D.
chemical energy
potential energy
thermal energy
kinetic energy
Essay
1. What is the difference between velocity and acceleration? How are they related?
2. A baseball player throws a baseball a distance of 30 meters (m). The ball takes 3 seconds (s) to reach
another player. State the average speed of the ball, and explain how you figured this out