Download 21.ForcesReview

TEST REVIEW - Physics – Forces
Name: ___________________________
CONCEPTUAL QUESTIONS- provide complete responses.
FREE RESPONSE QUESTIONS: You must list your givens for each problem to receive full credit.
LT#1: Identify the types of forces acting on an object.
1.
What is the difference between a contact force and an action-at-a-distance force? Give an example of
each.
2.
When is an object in equilibrium? What is the difference between dynamic and static equilibrium?
Give an example of a scenario of each kind of equilibrium.
3.
Construct free-body diagrams for the following situations. Label the forces according to type and draw
the arrows such that their length reflects the magnitude of the force.
a. A falling skydiver is speeding up.
b. A falling skydiver has reached a terminal velocity.
c. After reaching a terminal velocity, a falling skydiver has opened her parachute.
LT#2: Describe the relationship between force and acceleration
1. A tractor accelerates from rest to 13 m/s in 6.0 seconds.
a. What is the acceleration of the tractor (hint: list your givens and think kinematics!)? [2.167 m/s2]
b. What is the net force on the 145 kg tractor? [314.2 N]
2. A crate is accelerating at a rate of 3 m/s2. If the net force on the crate is doubled and the mass of the
crate is cut in half, what is the new acceleration of the crate?
LT#3: Relate net force to the type of motion and solve for net force.
1. Which one(s) of the following force diagrams depict an object moving to the right with a constant speed? List
all that apply.
2. Without friction, if you are coasting (no applied force), your acceleration is ______ and your velocity is
_________________.
3. Two horizontal forces, 350 N and 100 N are exerted in the same direction on a crate. Find the net horizontal
force on the crate.
car using cruise control.
for car gaining speed as it moves
away from a stop sign.
Free Body Diagram
What is the net force?
Is the car accelerating?
4. Your hand exerts 6.5 N upward on a pound of sugar. Considering the force of gravity on the sugar, what is
the net force on the sugar? Give the magnitude and direction of the net force. (1 lbs = 4.45 N)
LT#4: Explain the difference between mass and weight.
1. What is the difference between mass and weight? What are the units of each?
2.
Little Billie weighs 360 N on Earth. What is Little Billie's mass on the moon where the gravity is
approximately 1/6-th that of Earth's? ________ .
3.
Which of the following statements are true of the quantity mass? List all that apply.
a. The mass of an object is dependent upon the value of the acceleration of gravity.
b. The mass of an object is variable and dependent upon its location.
c. If all other variables are equal, then an object with a greater mass would have a more difficult
time accelerating.
d. The mass of an object is mathematically related to the weight of the object
4.
Which of the following statements are true of the quantity weight? List all that apply.
a. The weight of an object would be less on the Moon than on the Earth.
b. A person could reduce their weight significantly by taking an airplane ride to the top of Mount
Everest.
c. Two objects of the same mass can weigh differently.
d. To gain weight, one must put on more mass.
5.
a. What is the weight of a 35 kg cat on Earth? [343 N]
b. If the cat went to the moon, where gravity is 1/6 that of Earth, what would be her mass? Her weight?
[35 kg, 57.2 N]
LT#5: Describe the two types of friction and solve problems involving friction.
1. What is the formula to determine the coefficient of friction?
2. Why does your foot slide easier on smooth ice than on dry concrete when you apply the same force?
3.
Which is greater, static friction or kinetic friction? Give an example of when static friction is useful in
everyday life.
4.
What factors affect the force of friction on an object?
What factors do NOT affect the force of friction on an object?
5.
A 250 N box of mail is being slid along the floor at a constant velocity by a horizontal force of 98 N.
a. What is the force of friction on the box? [98 N]
b. What is the coefficient of friction between the box and the floor? [.392]
6.
A 15 kg book is pushed with a force of 45.6 N across a table at a constant speed.
a. Draw a free body diagram on the book. What is the coefficient of friction on the book? [.31]
b. If the book is then pushed with a force of 60 N, what is the acceleration of the book? Draw a new free
body diagram. [.96 m/s2]
c. If two books are pushed across the table instead of just one with the same 60 N force, what would be the
result? [compare the force of friction to the pushing force!]
7. A sled with a mass of 20 kg is pulled along a flat snow covered ground. The static friction coefficient is 0.22
and the kinetic coefficient is 0.13.
(a) How much does the sled weigh?
(b) What force is needed to get the sled moving?
LT#6: Determine how acceleration affects your weight.
1. Construct free-body diagrams for the following situations. Label the forces according to type and draw the
arrows such that their length reflects the magnitude of the force.
a. An upward moving elevator (held by a cable) slows down
b. A downward moving elevator (held by a cable) slows down.
2. You, with a mass of 95 kg, are standing on a scale while riding an elevator. What would the scale read in
Newton when:
a. The elevator accelerates at 2 m/s2 while moving upward?
b. The elevator accelerates at 2 m/s2 while moving downward?
c. The elevator travels upward at a constant rate?
d. The elevator travels down at a constant rate?
LT#7: Identify and explain Newton’s 3 laws of motion.
Describe each of Newton’s Three Laws of Motion and give an example of each.
LAW
DESCRIPTION of the LAW
EXAMPLE
#1
#2
#3
Other Things to Study: jigsaw ?s, foldable, quizzes, F=ma & Friction HWs, Equilibirum Practice Prob