Download Newton`s Laws of Motion Midterm Review

Review 2010
PART 3: Newton’s Laws of Motion
Newton’s Laws of Motion Midterm Review
1. Fill in the following table
Variable
Description
(words)
Acceleration
Change in
velocity
Mass
Inertia
Amt of matter
in a body
Equation (if
applicable)
Scalar or
vector?
Units
Example
F/m = a
Vector
m/s2
A change from 3 m/s to
6 m/s in 1 second is an
acceleration of 3 m/s2
F/a = m
Scalar
Kg
Scalar (1st yr
physics
students)
Kg (same as
mass)
F = ma
Vector
Newtons
Weight =force
= mass*g
Scalar
Newtons
A person has a mass of
23 kg and a weight of
230 Newtons
Inertia is proportional to
mass. It is a measure of
the resistance to
changes in velocity.
The cart accelerated
when acted upon by a
constant force.
The weight of an object
is always its mass*g
Resistance to
change in its
state of motion
(Newton’s 1st)
Force
A push or a pull
Weight
Weight
depends on the
force of
attraction
between the
earth and
another object
Or
F = ma
Weight = mg
Gravity is a force toward
the center of the earth
which causes an object
to accelerate at 10 m/s2
2. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose an astronaut in
that place throws a rock. The rock will (Choose one):
a. gradually stop
b. b. continue in motion in the same direction at constant speed
3. What will happen to the rock if a constant force is applied in the opposite direction?
a. it will slow down and switch directions
b. it will stop immediately
c. nothing
4. An 2-kg object is moving horizontally with a speed of 4 m/s. How much net force is required to keep the
object moving with the same speed and in the same direction?
a. 8 Newtons
b. 80 Newtons
c. 0 Newtons
5. An elephant and a mouse would both have zero weight in gravity-free space.
a. Which one has more inertia? _________elephant____________
b. Which one has a greater tendency to keep moving? _Elephant____________________
c. Which one would take a greater force to stop? ___niether – depends on time to stop and how
fast they are going__________________
6. What is the difference between mass and weight?
a. Mass changes as the gravitational force changes
b. Weight changes as gravitational force changes
c. Mass is independent of the gravitational force
d. Both b and c
7. What is the weight of 2 kg of cheese sitting in front of this classroom?
a. ~2 kg
b. ~2 N
c. ~20 N
d. Cannot answer due to insufficient information
8. Draw and label free body diagrams for:
a book accelerating across a table
Tarzan hanging on a vine
9. Units of mass? ___kg______ Units of force? ____N_____ Units of acceleration?__m/s/s_______
10. Does a force always result in movement? Why or why not?
no, only a net force results in a net acceleration.
11. A net force of 16 N causes a mass to accelerate at the rate of 5 m/s2. Determine the mass.
3.2 kg
F = ma m = F/a
2
12. An object is accelerating at 2 m/s2. If the net force is tripled and the mass of the object remains the
same, what is the new acceleration? 6 m/s/s
13. Suppose you wish two objects to accelerate at the same rate. One object has a mass of 6 kg, and one
has a mass of 3kg. How much greater must the force on the 6 kg mass be to keep the acceleration the
same?
Twice
14. For the free body diagrams, fill in the missing forces if the net force is as follows.
Net Force Left = 50N
Net Force Up = 5 N
Net force right = 20 N
Net force down = 40 N
a. _20__N
50 N
50 N
b.
_100
__ N
20 N
c.
0_N_
_N
15 N
d. _90____N
15. What is the magnitude and direction of the net force acting in each case below.
55 N
10N
4N
10 N
25 N
16. Magnitude: _____30 N________
Direction: _____Up_________
7N
5N
4N
Magnitude: _____2 N________
Direction: _______Right_____
17. While driving, Anna Litical observed a bug striking the windshield of her car. The bug hit the windshield
and the windshield hit the bug. The force is greater on:
a. The windshield
b. The bug
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c. Neither, the force is equal
18. A gun recoils when it is fired. The recoil is the result of action-reaction force pairs. As the gases from the
gunpowder explosion expand, the gun pushes the bullet forwards and the bullet pushes the gun
backwards. On which object is more force exerted?
a. The gun
b. The bullet
c. they are equal
19. Which object experiences the greater acceleration, the gun or the bullet?
a. The gun, because it has more mass
b. The bullet because it has less mass
20. If the net force acting on a cart increases 5 times, the acceleration will:
a. double
b. decreases to 1/5th
c. increases 5 times
d. increase 50 times
21. If a certain net force accelerates a car 8m/s2, what will the NEW acceleration be for the same net force
on the car if it is loaded with passengers and the car's entire mass doubles?
a. no acceleration
b. 8 m/s2
c. 2 m/s2
d. 4 m/s2
22. The more mass an object has, the more inertia it has. This statement is:
a. Always True b. Sometimes True and Sometimes False c. Never True
23. A parachuter jumps out of a plane and after some time, pulls the cord and the parachute is released.
The jumper has an upward force of air resistance of 1800N, while she has a force of gravity of 1000N. At
this time the parachuter will be:
a. not moving at all b. falling and getting slower c. falling and getting faster
d. moving up
24. A 5 kg block is accelerated upward by a rope at a rate of 2 m/s2. Answer the following:
a. Draw a FBD of the block.
b. Calculate the force of gravity on the block.
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c. Calculate the net force on the block.
d. Calculate the tension in the rope.
25. Match the following forces with their definitions:
Applied Force
Normal Force
Friction
Air Resistance
Tension:
Gravity
Air Resistance
Applied Force
Friction
Gravity
Normal Force
Tension
Resistance force that occurs as molecules of the atmosphere push back against an
object moving through the atmosphere
Force exerted on one object by another object or person
Force exerted on an object as it is moved across (or attempted to be moved across)
another object)
Force with which masses attract each other
Support force exerted when one object is in contact with another
Force which is transmitted through a string, cable, rope or wire when it is pulled tight
by forces acting at both ends
23. Static friction occurs when an object is _____not_________ in motion, while kinetic friction is the
friction that occurs while the object ____is_______ in motion relative to another body it is in contact
with.
24. An object that has a net force exerted on it must be
a. at rest
b. moving constantly
c. accelerating
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