Download Science Study Guide: Matter in Motion How can you determine that

Science Study Guide:
Matter in Motion
1. How can you determine that an object is in motion? What are reference points?
 You know if an object is in motion by comparing its distance to certain reference
points
 a reference point is a point that you refer to, to track motion in objects
2. Compare and contrast speed and velocity. Know how to solve problems for both. What
is the difference between constant speed and average speed?
 Speed is distance traveled in a certain amount of time… velocity includes speed and
directs
 Constant speed only occurs when an object does not accelerate and no opposing
forces act upon the object
 Average speed is the average of all the speeds an object moved at
 Velocity is equal to speed + direction (60 mph east)
 Speed= distance/time …. 5 in/sec
3. When is a resultant velocity the result of adding and when is it the result of subtracting?
 It is a result of adding when two objects are moving in the same direction
 It is a result of subtracting when the objects are going different directions
4. Describe what is necessary for an object to accelerate. Explain the meaning of the units
used for acceleration (what is 5m/s/s telling you?). Know how to solve problems dealing
with acceleration. What is the meaning of negative acceleration?
 A change in velocity is necessary for an object to accelerate
 The unit of acceleration is telling us, for example, in 5 m/s/s that an object will
accelerate 5 meters per second for every second it travels.
 Acceleration= (finishing velocity- initial velocity)/time
 Negative acceleration occurs when an object is slowing down
5. What is a force? In what unit is it measured? When is net force the result of adding and
when is it the result of subtracting?
 A force is a push or pull
 Measured in N
 Net force is the result of adding when two forces are applying force in the same
direction
 Net force is the result of subtracting when the two forces are being applied in
opposite directions
6. Describe balanced and unbalanced forces. Which results in a change of motion? In
which direction does an object with unbalanced forces move?

Balanced forces are two forces that equal out so that the object they are applying
force to isn’t moving
 Unbalanced forces are two forces that are applied to an object that causes it to move
 Unbalanced forces result in a change of motion
 If unbalanced forces are pushing towards each other, the object will move towards the
weaker force
 If unbalanced forces are pulling away from each other, the object will move towards
the stronger force
7. Describe friction. When does it occur? Give actual examples of friction. When is it
beneficial? When is it not beneficial? How can friction be increased or decreased? In
what unit is it measured?
 Friction is a force that opposes motion when two objects touch
 It occurs when two objects rub against each other
 Examples: air resistance, brakes, car engine, bicycle chains
 Helpful… keeps us from slipping and sliding everywhere, friction between your
pencil and paper
 Harmful… can cause parts in a car to heat up, cause holes in our socks, can cause
bike chains to become defective
 Can be increased by making surfaces rougher and adding force pushing objects
together
 Can be decreased by using lubricants, switching to rolling friction, and making
objects smoother (sandpaper)
 Factors of friction are… the smoothness of the surfaces and the force applied to the
surfaces
8. Know kinetic and static friction.
 Kinetic friction is moving friction/friction between moving surfaces
 Kinetic friction can be broken up into rolling and sliding friction. Rolling friction
occurs when an object has wheels. It is usually less in force. Sliding friction occurs
between objects that aren’t round.
 Static friction is friction caused by objects that have no movement.
 An example of static friction is when the leg of your desk is touching the floor.
9. State Newton’s Law of Gravitation. Why is it a ‘universal’ law?
 The strength of gravity depends on mass… distance affects the gravitational attraction
between objects
 It is a universal law because it is true for everywhere in the universe
 The normal gravitational pull on Earth is 1g.
10. Know the difference between weight and mass.
 Weight is a measure of gravitational pull on an object… measured in lbs., kilograms,
grams, etc. It is measured with a spring scale


Mass is the amount of matter in an object. It is measured in Newtons. It is measured
with a triple beam balance.
100g = 1N