Newtonian Physics

Newton's First Law

an object stays at rest/in motion unless acted on by an outside force

Newton's Second Law

F=ma

Newton's Third Law

in an interacting pair, the force exerted on one is equal in magnitude and opposite in direction to the force exerted on the other

When do Newton's laws apply?

in an inertial reference frame

When do Newton's laws not apply?

in a non-inertial reference frame, for very massive or very light objects

What is the kinematic chain?

velocity is the derivative of displacement, acceleration is the derivative of velocity

Newtonian or Aristotelian: If you push on something, it moves. If you push twice as hard, it moves twice as fast.

A

Newtonian or Aristotelian: ) A heavy object falls faster than a light object

A

Newtonian or Aristotelian: The moon is held in its orbit around the earth by the force of the earth's gravity

N

Newtonian or Aristotelian: If you push on an object, it moves. After you release it, it gradually comes to rest because friction drains away the force of the initial push.

A

Newtonian or Aristotelian: The speed of a falling object increases as it falls.

B

A spaceship with a mass of 20,000 kg is traveling in a straight line at a constant speed of 300 km/s in deep space. Its rockets engines must be: (A) off or (B) firing?

A

When an object travels with constant velocity in a straight line its acceleration is:

0

A 6-kg bowling ball moving at 3 m/s collides with a 1.4-kg bowling pin at rest. How do the magnitudes of the forces exerted by the collision on each object compare?

Both objects experience the same magnitude of force

A large car drags a small trailer in such a way that their common speed increases rapidly. Which tugs harder on the other?

Both tug equally on each other.

If two objects connected to each other accelerate at the same rate, the amount of force each object exerts on the other is:

equal

A parent pushes a small child on a swing so that the child moves rapidly away while the parent remains at rest. How does the magnitude of the force that the child exerts on the parent compare to the magnitude of the force that the parent exerts on the child?

The forces have equal magnitudes

Instantaneous velocity is:

how fast an object is moving at a given time

Average velocity is:

displacement/time

An object can have a constant speed and still be accelerating if:

it changes direction

An object's acceleration vector always points in the direction that it is moving. T or F?

F

An object can have zero velocity (at an instant) and still be accelerating. T or F?

T

An object's x-velocity can be positive at the same time that its x-acceleration is negative. T or F?

T

A ball is thrown upward. At its highest point, its velocity is:

0

A ball is thrown upward. At its highest point, its acceleration is:

downward

A ball is thrown upward. At its highest point, its gravitational force is:

downward

Direction of velocity of an object in orbit is:

tangent to the orbit

Direction of acceleration of an object in orbit is:

toward the center

Direction of gravitational force of an object in orbit is:

toward the object it is orbiting

Direction of net external force of an object in orbit is:

toward the object it is orbiting

Direction of gravitational force of an object being orbited is:

toward the object orbiting it

You push a crate, but it does not move. What is the force of static friction on the crate compared to the force of your push?

equal

A car moving at constant speed travels through the lowest point in a circular valley. What is the car's acceleration at this point?

upward/toward the center

A constant negative slope on a position graph means the object is:

moving constantly negative

A positive horizontal line on a velocity graph means the object is:

moving at constant velocity positive

A horizontal line at 0 on a velocity graph means the object is:

at rest

A positive increasing line on a velocity graph means the object is:

accelerating positive

To determine which string holding a hanging object exerts the greatest force:

think of strings as sides of triangles

The magnitude of the normal force on a box sitting on an incline is equal to that of its weight. T or F?

F

A thrust force from its propeller pulls a plane forward; a drag force pushes it backward. Is this a third law pair?

no

A car exerts a forward force on a trailer; the trailer tugs backward on the car. Is this a third law pair?

Yes

A motorboat propeller pushes backward on the water; the water pushes forward on the propeller. Is this a third law pair?

Yes

Gravity pulls down on a person sitting in a chair; the chair pushes back up on the person. Is this a third law pair?

No

A third law pair

forces act in equal but opposite pairs on the same pair of objects

At the bottom of a circular path, an object’s normal force is

greater than the force of gravity

An inertial reference frame is

moving at a constant velocity

A non inertial reference frame is

accelerating

When a projectile falls from a moving vehicle, its horizontal velocity is

constant

As a projectile moves along is parabolic trajectory, what remains constant (ignoring air resistance, and defining the z axis as pointing upward?

x velocity, y velocity, acceleration

If you double the amplitude of a harmonic oscillator, the oscillator's speed

does not change

Kepler's second law implies that as a planet's distance from the sun increases in an elliptical orbit, its orbital speed

decreases

In circular motion, acceleration and net force always point towards:

the center

A box sits at rest on an inclined plank. How do the magnitudes of the normal force and the gravitational force exerted on the box compare?

Fn < Fg

If we know an object is moving at constant velocity, we may assume

the net force acting on the object is zero

At the very bottom of a valley, how does the magnitude of the normal force on a car compare to the magnitude of the car's weight?

Fn \> Fg

When a road is banked...

normal force increases

If an object is at rest, net force is

0

The net torque on an object must also be___ if it is at rest

0

Torque ___ the force of the object it is acting on

opposes

The period of an oscillation is

The amount of time it takes to complete a full oscillation

The frequency of an oscillation is

the number of oscillations in the one-time unit

The phase rate of an oscillation is

2pi/T

The initial phase of an oscillation is

its y position at t=0

In nonuniform circular motion

speed is not constant

Kepler's 1st Law

the planets orbit in an ellipse

Kepler's 2nd Law

a line from the planet to the sun sweeps out equal areas of equal intervals of time

Kepler's 3rd Law

p^2=a^3

The direction of drag force is always

vertical

If an object leaves a noninertial reference frame, it moves

tangential

During free fall acceleration is

constant