College Physics Exam 2
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135 Terms
Force
push or pull, on an object by another object
Most forces are
contact forces
Is a force a vector or scalar?
vector; direction matters, you can add them as vectors & the net force is a sum of forces
Non-contact forces
gravity (CPZ - electric, magnetic)
Inertia
property of an object (not a force) that resists a change in motion; related to the number of atoms
Inertia is measured as
mass (kg)
Newton's 1st Law
law of inertia; if there's no force on an object (or the net force of zero) then object's motion is constant
N1 velocity & acceleration "rules"
v constant a=0; v=0 is constant; v constant until F acts on object; v constant if Fnet=0 a=0
Weight force
w; force of gravity on the mass of an object
Normal force
n; force of surface on an object, perpendicular to the surface
Friction force
f; parallel to surface; kinetic (opposite motion) & static (oppose motion)
Spring force
stretch/compress & returns to original shape
Newton's 2nd Law
law of motion; a=Fnet/m
Newton's 3rd Law
law of force pairs; every interaction has 2 forces one force on each object; same magnitude but opposite direction
Equilibrium
a=0; static v=0 & dynamic v is constant
N's 1st Law explains
uniform motion
Apparent weight
force supporting an object (n)
Normal force: a parallel to n then
n doesn't equal w
2 multiple choice options
Normal force: a same as n then
n > w
2 multiple choice options
Normal force: a opposite as n then
n < w
2 multiple choice options
Period (T)
time for circuit
Speed (v)
circumference/period; 2(pi)r/T
Frequency (f)
revolutions per second
One full rotation
2(pi)r
Position (linear; rotation)
x,y, delta x (m); theta (radians)
Velocity (linear; rotation)
Vx, Vy (m/s); curvy w (angular v rad/s)
Acceleration (linear; rotation)
ax, ay (m/s^2); alpha (angular a rad/s^2)
The tendency of an object to resist a change in its motion is known as
Inertia
3 multiple choice options
Newton's first law says
An object's velocity will be constant (both speed & direction) as long as no force acts on it
3 multiple choice options
The frictional force is
Parallel to the surface the object is on
3 multiple choice options
The normal force is
The force of a surface on an object that is perpendicular to the surface
3 multiple choice options
The acceleration of an object has what kind of relation to the mass of the object?
Inverse
3 multiple choice options
Which of these is a part of the definition of a force?
All of these are part of the definition of a force
3 multiple choice options
The symbol used for a frictional force is
f
3 multiple choice options
Dynamics, or the study of forces, is the study of
The causes of motion
3 multiple choice options
The gravitational force of the Earth on an object close to the surface is also known as
Weight
3 multiple choice options
The acceleration of an object has what kind of relation to the force applied?
Linear
3 multiple choice options
The net force on an object is
In the same direction as the acceleration
3 multiple choice options
If the net force on an object is zero, what can be said about the vectors on a free body diagram
The vector sum is zero
3 multiple choice options
A free body diagram should include
All of these
3 multiple choice options
The other force in the action/reaction pair of a hammer striking a nail in a wall is
The force of the nail on the hammer
3 multiple choice options
The net force on an object is
The vector sum of all the forces on the object
3 multiple choice options
Which of these is not a unit of force?
All of these are units of force
3 multiple choice options
When a cat jumps from the floor onto a table, what can be said about the force on the floor
The force of the floor on the cat is equal to the force of the cat on the floor
3 multiple choice options
An example of a long-range force is
Weight
3 multiple choice options
Newton's 3rd law says
All forces occur as a part of an action/reaction pair
3 multiple choice options
How are acceleration & force related?
Acceleration is directly proportional to force
3 multiple choice options
How are the mass (m) & weight (w) of an object related?
w = mg
3 multiple choice options
An object near the Earth seems 'weightless' if
It is in free fall
3 multiple choice options
How can the apparent weight of an object be measured?
A simple scale
3 multiple choice options
Riding in an elevator, when is your weight different than your apparent weight?
Any time an elevator's speed is changing
3 multiple choice options
The y component of an object's acceleration is determined by
The y components of all the forces on the object
3 multiple choice options
The acceleration in the x-direction is determined by the
Sum of the x-components of all forces acting on the object
3 multiple choice options
If an object is in equilibrium, what does Newton's 2nd law tell us?
The net force is zero
3 multiple choice options
What can be said about the net force on an object when its velocity is changing?
Net force is in the same direction as the acceleration
3 multiple choice options
Is the net force larger when an object is in static equilibrium or dynamic equilibrium?
Net force for both is zero
3 multiple choice options
An object in dynamic equilibrium is
Moving with a constant velocity
3 multiple choice options
Is the normal force affected by any other forces?
Yes, it is changed by forces that are parallel to the normal force
3 multiple choice options
The Reynolds number is used to characterize
The types of drag an object experiences
3 multiple choice options
Hook's Law says the force of a spring
This is not in this chapter
3 multiple choice options
Terminal speed occurs when
The drag force is equal in magnitude to the weight
3 multiple choice options
How does the coefficient of static friction usually compare to the coefficient of kinetic friction?
Static > kinetic
3 multiple choice options
Which of these does the kinetic frictional force not depend on?
Speed of the motion
3 multiple choice options
Drag on an object moving through a fluid depends on
All of these
3 multiple choice options
In order for a bicycle wheel to roll on the street the bottom of the wheel must
Be stationary
3 multiple choice options
When trying to slide an object on a rough surface, what requires a larger force?
Getting it started
3 multiple choice options
The normal force on an object is always
Perpendicular to the surface the object is in contact with
3 multiple choice options
Which of Newton's laws are important for analyzing interaction objects?
The 2nd & 3rd laws
3 multiple choice options
When analyzing an interaction involving three interaction objects how many FBDs need to be drawn?
3 - one for each object
3 multiple choice options
What approximations are made when dealing with pulleys & ropes in chapter 5?
The pulley is frictionless, & the pulley & string are both massless
3 multiple choice options
When two objects are connected by a string how are the tension forces on each object related?
The tension forces on each object are the same
3 multiple choice options
When an object's velocity is decreasing
The net force & the acceleration are opposite the motion
3 multiple choice options
The kinetic frictional force is proportional to
The normal force on the object
3 multiple choice options
When objects are in contact with each other & moving together how are the accelerations of each object related?
They have the same acceleration
3 multiple choice options
The electric force of a proton on an electron
Is not in this chapter
3 multiple choice options
How does a massless, frictionless pulley change the tension in a string?
Changes the direction of the tension
3 multiple choice options
If the velocity of a moving object is not changing, then
The net force is zero
3 multiple choice options
At what point on a roller coaster loop is your apparent weight the greatest
Bottom
3 multiple choice options
How are period (T) & frequency (f) in circular motion related?
T = 1/f
3 multiple choice options
How does banking a curve on the highway allow cars to drive at a higher speed in the curve?
The normal force provides some centripetal acceleration
3 multiple choice options
A car driving around a corner at a constant speed has
Acceleration toward the center of the curve
3 multiple choice options
What is the force, F, needed to keep an object with mass m in a circular path with radius r at a constant speed v?
F = mv^2/r
3 multiple choice options
The time for an object to complete one revolution is called the
Period
3 multiple choice options
According to the book, your maximum walking speed is determined by
The length of your leg
3 multiple choice options
The maximum safe speed to turn a corner depends on
The static friction between the tires & the road
3 multiple choice options
The centrifugal force
Is not an actual force
3 multiple choice options
The critical speed for traveling around a vertical loop
All of these are correct
3 multiple choice options
The speed of a satellite in a circular orbit around a star does not depend on
The mass of the satellite
3 multiple choice options
The acceleration due to gravity near the surface of the moon depends on
The mass & radius of the moon
3 multiple choice options
The period of a satellite orbiting a planet does not depend on
The mass of the satellite
3 multiple choice options
A satellite is in a circular orbit around the Earth. What mass(es) does the orbital speed depend on?
Mass of the Earth only
3 multiple choice options
As the distance between 2 objects increases, what happens to the force of gravity between them?
The force decreases
3 multiple choice options
The feeling of weightless near the Earth means
The object is in free fall
3 multiple choice options
Which of these is in free fall around the Earth?
All of these are in free fall
3 multiple choice options
An object in orbit around the Earth
Is in free fall
3 multiple choice options
Newton's Law of Gravity says the gravitational force between 2 objects is related to the distance, r, between them as
1/r^2
3 multiple choice options
Two planets have the same mass, but planet X has twice the radius of planet Z. How does the acceleration due to gravity compare between the two?
Acceleration due to gravity is larger on Z
3 multiple choice options
Newton's Law of Gravity says the gravitational force between two objects is proportional to
1/r^2
3 multiple choice options
The center of gravity of an extended object
Can be calculated from the center of gravity of individual pieces of the object
3 multiple choice options
Torque depends on
All of these are correct
3 multiple choice options
