Work, Energy, Power and Momentum

Question 1

When looking at change in momentum problems

Answer 1

Pay attention to the direction of velocity

Question 2

If work is performed by a net force

Answer 2

W= ΔKE

Question 3

Formula for weight

Answer 3

W = mg

Question 4

Formula for Potential Energy

Answer 4

PE = mgh

Question 5

When approaching an elevator problem where you’d feel lighter

Answer 5

Subtract acceleration to gravity

Question 6

Hooke’s Law

Answer 6

F = -kx

Question 7

Formula for force of gravity

Answer 7

Fg = F (m1m2/r^2)

Question 8

Which situations should be treated as elastic collisions

Answer 8

If objects bounce off each other during collisions

Question 9

Static Friction

Answer 9

Object is not moving

Question 10

What kind of work is done when an object moves up

Answer 10

Negative, against gravity

Question 11

Newton’s second law

Answer 11

Sum of the forces always equals m*a

Question 12

Elastic Potential Energy Formula

Answer 12

P.E.e = 1/2kx^2

Question 13

Formula for Work

Answer 13

W=Fdcosθ

Question 14

Units for Work

Answer 14

J/Kgm/Kgm^2/s^2

Question 15

Impulse

Answer 15

The product of the force and the time for which the force is applied

Question 16

What kind of work is done when holding stationary objects?

Answer 16

No work is done when holding stationary objects. Without displacement work done is zero

Question 17

Both masses united by one rope will have the same acceleration and tension

Answer 17

Find out which force wins and calculate the acceleration using their combined masses.

This does not work for tension

Question 18

Elastic Collisions

Answer 18

Both the momentum and the kinetic energy are conserved.

Question 19

Inellastic Collisions

Answer 19

Total kinetic energy of the system is not conserved

Question 20

When friction is ignored the total mechanical energy in a system

Answer 20

Remiains the same

Question 21

What is the relationship between mass and velocity

Answer 21

The speed of a falling object is not dependent upon its mass. We don’t need to know the mass to determine the final velocity

Question 22

Formula’s for Impulse

Answer 22

FΔt = Δp or FΔt = mΔv or FΔt = m(vf – vi)

Question 23

How does the momentum of an object change

Answer 23

Anytime its velocity or mass changes

Question 24

Formula’s for Power

Answer 24

P= (W/t) = (fd/t) = fv

Question 25

Linear momentum

Answer 25

p=mv

Question 26

Conservation of Momentum general formula for two objects

Answer 26

m1v1i + m2v2i = m1v1f + m2v2f

Question 27

Newton’s third law

Answer 27

For every force exerted by one bisect on a second object, there is an equal but opposite force by the second object

Question 28

What happens to the Normal force when you press down on an object

Answer 28

It increases since there is more friction

Question 29

Newton’s first law

Answer 29

An object’s velocity remains constant unless a force is acting upon it If the sum of the forces equals zero then velocity is constant

Question 30

Mechanical Energy is conserved if

Answer 30

No work is done by no conservative force (friction, air resistance, etc.)

Question 31

Formula for Mechanical Energy

Answer 31

E = KE + PE

Question 32

If work is performed by none conservative forces

Answer 32

Wnc = ΔE

Question 33

For questions that ask you to calculate the change in momentum of a single object, where the mass of the object does not change use

Answer 33

Δp = pf – pi = mvf – mvi = m(vf – vi)

Question 34

Centripital force formula

Answer 34

Fc = (mv^2/r) = mac

Question 35

Formula for Gravitational Potential Energy

Answer 35

P.E. = mgh

Question 36

When on a horizontal plane the normal force and weight will

Answer 36

Equal each other. Not the case on an incline plane

Question 37

Because mechanical energy in a system is conserved in problems where you are given a few known variables

Answer 37

You can set P.E. = K.E.

Question 38

Mechanical Energy

Answer 38

The sum of the kinetic energy and all forms of potential energy in the system

Question 39

Formula for Kinetic Energy

Answer 39

KE = 1/2(mv^2)

Question 40

When apporaching an elevator problem where you’d feel heavier

Answer 40

Add acceleration to gravity

Question 41

Which situations should be treated as inellastic collisions

Answer 41

Objects remain in contact after the collision

Question 42

Centripial acceleration formula

Answer 42

ac = (v^2/r)

Question 43

What relationship does the force an object experiences have towards the time that force acts

Answer 43

It’s inversely proportional. i.e. That means that if it takes longer for an object to come to a stop, it will experience a smaller instantaneous force

Question 44

Formula for force of friction

Answer 44

Ff = μN

Question 45

Kinetic Friction

Answer 45

Object is sliding accross the surface