Download Third Grade Study Guide

Third Grade Study Guide
Forces and Motion Test
Test Date: October 24, 2008
Study this information for our forces and motion unit test. Study everything because a variety of
questions will be on your test.
A Force is a push or pull.
Balanced forces are equal and an object doesn’t move.
Unbalanced forces are unequal and the object moves in the direction of the stronger
force.
Motion is a change in position.
Speed is the measure of how fast something moves over a certain distance.
Gravity is a force that pulls us, and everything around us, down.
Weight is a measure of the pull of gravity on an object.
Work is the measure of force it takes to move an object a certain distance.
*Remember work has nothing to do with a job you are doing.
*Work is done only when an object is moved over a distance.
A System is a group of parts that work together as a unit. Simple Machines are systems that
may work alone or are a part of a larger system.
A Simple Machine is a tool that helps people do work. It doesn’t change the amount of work.
It just makes the work seem easier.
The Six Simple Machines are: the lever, the pulley, the wheel and axle, the inclined
plane, a wedge, and a screw.
A Lever is a bar that moves on or around a fixed point. Example: a seesaw.
Wheels and Axels are turning levers. The force needed to move an object decreases as
the Wheel gets larger. Example: a pencil sharpener.
A Pulley is a rope over a Wheel. It changes the direction of the force you use.
Example: a flagpole.
An Inclined Plane is a flat surface set at an angle to another surface. Example: a ramp.
A Wedge is two inclined planes stuck back to back. Example: a doorstop.
A Screw is an inclined plane wrapped around a shaft. Example: a jar lid.
Isaac Newton (1642 - 1727) was an English scientist who described the Three Laws of Motion.
Three Laws of Motion (a summary):
1. An object will not move until a force acts upon it. (For example, the checker would not
move until you pushed it.)
An object will keep moving until a force acts upon it. (For example, the checker kept
moving until the force of friction stopped it.)
2. An object will move in the direction of the greater force. (For example, in tug of war, the
team with greater force pulls the other team towards them.)
The greater the mass the less acceleration the object will have. (For example, the
baseball with less mass accelerated more when rolled.)
3. For every action there is an equal and opposite reaction. (For example, when we bounced
the ball down to the floor, the ball bounced back with equal force.)
SAMPLE QUESTIONS
Circle the Correct Answer.
1. Many things can produce a force. What is a force?
a. A Jedi’s power
b. A push or a pull
c. A tool
d. A mass
2. Who was Isaac Newton?
a. A president
b. An artist
c. An English scientist
d. A simple machine
3. Which one of these is NOT a simple machine?
a. A lever
b. Wheel and axel
c. A mushroom
d. An inclined plane
Screw
Motion
Push
System
Speed
Scientist
Use the words in the box to fill in the answers.
4.
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9.
__________ is a change in position.
A force is a _________or a pull.
A __________is a group of parts that work together as a unit.
Isaac Newton was a ___________.
An inclined plane wrapped around a shaft is a ___________.
The measure of how fast something moves over a certain distance is its __________.
10. In your own words, write one of the three laws of motion:
__________________________________________
__________________________________________
11. Sketch and label two (2) simple machines.
12. When we played tug-o-war in class, we showed that forces can be___________________
and _______________________.