What is the net force on an object when you combine a force of 15 N north with a force of 5 N south?
10N
100
In which of the following activities is friction harmful?
a. brakes stopping a car c. an eraser erasing
b. a person walking d. rough wood scratching your skin
d
100
Which of the following results in a helpful decrease of friction?
a. force applied while scrubbing c. sand applied to an icy road surface
b. oil added to a car engine d. deep tread added to snow tires
b
200
What term or phrase describes a point that appears to stay in place and can be used to detect the motion of an object?
reference point
200
What is a force?
a push or a pull on an object
200
True/False: pouring sand on ice reducing friction
false
200
Once an object starts moving, static friction is replaced by
What is kinetic friction
300
What are the two factors used to calculate average speed?
total distance and total time
300
What causes an object to start moving?
unbalanced forces
300
What is an example of an object opposed by static friction
A nonmoving box
300
Which of the following is least likely to be used as a lubricant?
a. air c. sand
b. motor oil d. grease
c
400
What causes a change in velocity?
a change in speed, a change in direction, or both
400
What is a force that opposes motion between two surfaces that are in contact?
friction
400
What are the two factors that affect the amount of friction between two surfaces?
the force pushing the surfaces together and the materials that make up the surfaces
400
The two properties that all forces have are
magnitude and direction
500
In which of the following examples is a skater NOT accelerating?
a. going straight while speeding up c. making circles at constant speed
b. going straight at constant speed d. going straight while slowing down
b
500
What balances the force of gravity on a hanging light?
tension
500
Which of these is opposed by kinetic friction?
a. a book sitting on a table c. a box sliding on a floor
b. a cat standing in a yard d. a child leaning on a building
c
500
If a hiker’s velocity begins at 1.8 m/s uphill and changes to 1.5 m/s uphill, how do you know that the hiker has a negative acceleration?
a. The direction changed. c. The speed increased.
b. The direction did not change. d. The speed decreased.