Transcript Ch 5-6 Test review

Chapters 5-6 Test Review
Forces & Motion
Forces
 “a push or a pull”
 A force can start an
object in motion or
change the motion
of an object.
 A force gives
energy to an object
What is a push or a pull?
 A. canopy
 B. force
 C. gruff
 D. scoff
Representing forces
 We often use arrows.
 Larger the arrow, the
greater the force
 Combined balanced
forces equal zero
 Normal force = the
force acting
perpendicular on an
object in contact with
another object.
What prevents a book on a table
from accelerating downward?
 A. gravity is pulling on the table
 B. the table is pushing back with a larger force
 C. the table is pushing back with an equal force
 D. air
Balanced Forces
 Forces opposite in
direction and equal in
size.
 Net result: no change
in motion.
Unbalanced Forces
 Unbalanced forces will cause an object to
change motion.
When an unbalanced force acts on
an object,
 A. the object’s motion does not change.
 B. the object accelerates.
 C. the object will stop.
 D. the inertia of the object increases.
The net forces acting on any object
will cause it to
 A. keep moving at the same speed.
 B. accelerate.
 C. stop.
 D. swim like a fish.
If a 10 N net forces acts on a 20 kg
object it will accelerate at (a=f/m)
 A. 5 m/s
 B. 200 m/s
 C. 0.5 m/s2
 D. 2 m/s2
What force is needed to accelerate a
4 kg ball at 12 m/s2? (a=f/m)
 A. 3 m/s
 B. 48 m/s
 C. 0.75 N
 D. 48 N
GRAViTY
The pull of
one body of
mass on
another.
What two factors change
gravitational force?
 A. Speed and direction.
 B. Mass and distance.
 C. Mass and velocity.
 D. Speed and momentum.
Weight is a force that depends on
gravity and
 A. mass.
 B. acceleration.
 C. friction.
 D. force.
Acceleration due to gravity
 All objects fall at the
same rate, regardless
of their mass or weight
 The acceleration due
to gravity on earth is
about 9.8 m/sec2.
 This value will change
with elevation and
location on earth.
Terminal Velocity
 After a period of
free fall, the force
of gravity will be
canceled by the
force of air friction
and objects will
travel at a constant
velocity
The forces acting on a falling leaf
are gravity and air resistance. If the
leaf falls at a constant rate,
 A. forces are balanced.
 B. forces are unbalanced.
 C. the world will end.
 D. a leaf never falls at a constant rate.
Newton’s First Law
of motion
 An object at rest will remain at rest and
an object in motion will remain in
motion unless acted upon by an outside
force.
 Often referred to as the Law of Inertia.
(the property of matter that resists any
change in motion)
The property of matter that resists
changes in motion is called
 A. centripetal motion.
 B. friction.
 C. inertia.
 D. projectile motion.
Inertia is related to
 A. speed.
 B. weight.
 C. mass.
 D. motion.
An orange might roll off your
cafeteria tray when you stop
suddenly because of
 A. the balanced forces acting on the orange.
 B. the friction forces acting on the orange.
 C. the centripetal force acting on the orange.
 D. the orange’s inertia.
Newton’s Second
Law of Motion
 The force of a moving object is directly
proportional to the object’s mass and
acceleration.
 The most important of Newton’s laws.
According to Newton’s second law,
the acceleration equals the net force
divided by the object’s
 A. mass.
 B. velocity.
 C. momentum.
 D. weight.
Weight and Mass
MASS
WEIGHT
 The measure of inertia
 A measure of the force
of an object.
 The amount of matter
in an object
 Stays constant with
changes in location
 A scalar
of gravity acting on an
object.
 Measured in newtons.
 Changes with changes
in location.
 A vector
Your weight equals your
 A. mass
 B. mass divided by the net force acting on it.
 C. mass times acceleration due to gravity.
 D. mass times your speed.
Why is your weight less on the
moon?
 A. Mass changes on the moon.
 B. Gravity is less on the moon.
 C. Gravity is greater on the moon.
 D. Weight never changes, only mass changes.
Newton’s Third Law
of Motion
 For every action there is an equal and
opposite reaction, or
 All forces occur in pairs
 examples:
Newton’s third law of motion
describes
 A. action and reaction forces.
 B. centripetal forces.
 C. balanced forces.
 D. net force.
When one object exerts a force on
another,
 A. the objects will always move as a result
of the interaction.
 B. an equal and opposite force is exerted
back on it by the other object.
 C. the objects will never move due to the
forces cancelling each other out.
 D. one object will always exert a greater
force on the other object.
Momentum
 All moving objects have momentum.
 How hard is it to stop and object.
 It is the product of an object’s mass and
velocity.
 the mass matters
 the speed matters
p = mv
What is the momentum of a truck at
rest?
 A. Zero
 B. Equal to the mass.
 C. Equal to the weight.
 D. Trucks do not need to rest.
If a golf ball and marble are rolling
at the same speed, which has a
greater momentum?
 A. Golf ball
 B. Marble
 C. They have the same.
 D. I lost my marbles a long time ago!
The product of an object’s mass and
velocity is its




A. centripetal force.
B. net force.
C. momentum.
D. weight.
P = mv