1. Benchmark and Reading Check Q & A:
Chapter 18
Standardized Test Preparation
Benchmark and Reading Check Q & A:
1. Pg 563: How does gravity differ from friction?  
Answer to Benchmark Check:
Unlike friction, gravity can act between objects that are not touching. 
2. Pg 564: How does mass affect gravitational force?
Answer to Reading Check:
Gravitational force increases as mass increases. (Note: Gravitational force increases as the mass of one or both of the objects increases.)
3. pg 566: Name 2 forces that act at a distance: magnetic, and electric, OR gravity.

2. Chapter 18 Ch. Review Q & A (570-571):
Standardized Test Preparation
Ch. Review Q & A ( ):
Opposes motion between surfaces that are touching.
Friction
2. The ________ is the unit of force.
Newton
3. _________is determined by combining forces.
Net force
4. Acceleration is the rate at which ________ changes.
velocity
5. If a student rides her bicycle on a straight road and does not speed up or slow down, she is traveling with a
b. constant velocity.

3. Chapter 18
Standardized Test Preparation
6. A magnet can exert a magnetic force on materials containing iron. Which of the following is an example of a magnetic force acting at a distance?
c. Magnets hold papers on refrigerator doors.
7. A hurricane is heading toward Florida. What information do you need to determine when the hurricane will
strike the coast?
d. the hurricane’s position, speed, and direction of motion
8. The gravitational force between 1 kg of lead and Earth is the gravitational force between 1 kg of marshmallows
and Earth.
c. equal to

4. Chapter 18 Which of the following is a measurement of velocity?
Standardized Test Preparation
Which of the following is a measurement of velocity?
c. 55 m/h south
10. Describe the relationship between motion and a reference point.
Motion occurs when an object changes position over time relative to a reference point (an object or location that appears to stay in place).
11. How is it possible to be accelerating and traveling at a constant speed?
A change in direction alone causes acceleration to occur.
Thus, no change in speed is necessary for acceleration to
occur.

5. Chapter 18
Standardized Test Preparation
Math Skills:
12. A kangaroo hops 60 m to the east in 5 s. Use this information to answer the following questions:
What is the kangaroo’s average speed?
12 m/s
b. The kangaroo stops at a lake for a drink of water and then starts hopping again to the south. Each second, the kangaroo’s velocity increases 2.5 m/s. What is the kangaroo’s acceleration after 5 s?
2.5 m/s2 south

6. Chapter 18 Applying Concepts:
Standardized Test Preparation
Applying Concepts:
13. Your friend asks to help move some boxes. One box is so heavy that you must push it across the room rather than lift it. How could you reduce friction to make moving
the box easier?
All reasonable answers. Sample answer: Use a handcart or dolly to take advantage of rolling kinetic friction, or polish the floor to reduce sliding kinetic friction.

7. Chapter 18 Analyzing Ideas:
Standardized Test Preparation
Analyzing Ideas:
14. Consider the scientific meaning of the word acceleration and the use of the term accelerator when talking about a car’s gas pedal. How can these meanings lead to confusion?
Sample answer: A driver uses a car’s gas pedal, which is called the accelerator, to increase the
car’s speed. This use of the term accelerator may cause
confusion by leading you to think that acceleration means only “speeding up.” However, the scientific meaning of the term acceleration includes slowing down and changing direction. (So, a car’s gas pedal is not the only device in the car that causes acceleration—the steering wheel could be called an accelerator, too!)

8. Chapter 18 Identifying Relationships:
Standardized Test Preparation
Identifying Relationships:
15. Explain why airplane pilots should know wind velocity as well as wind speed during a flight.
It is helpful for pilots to know wind velocity because velocity includes direction. Pilots need to know the wind’s speed and direction so that they will know whether the wind is blowing in the same direction that the plane is flying (which could increase the plane’s resultant velocity and lead to an earlier arrival time) or in a direction that differs from the direction in which the plane is flying (which might lead to a later arrival).