Physics

Question 1

When is work done on an object?

Answer 1

When a force causes a displacement of the object

Question 2

The force must be _____ to the displacement to do work.

Answer 2

Parallel

Question 3

If a student carries a bucket of water along a horizontal path while walking at constant velocity, what work is done?

Answer 3

0 because the force required to keep the bucket up is perpendicular to the horizontal displacement of the bucket.

Question 4

If there are many forces acting on an object, how do you find net work?

Answer 4

Wnet = Fnet * d * cos(angle)

Question 5

When is work positive?

Answer 5

When the direction of the force applied and displacement is the same. Speed gets bigger.

Question 6

When is work negative?

Answer 6

When the direction of the force , such as kinetic force, and displacement are opposite. The speed slows down.

Question 7

Kinetic energy

Answer 7

Associated with motion; m(v^2)2

Question 8

Net work done by a net force is equal to change in

Answer 8

kinetic energy

Question 9

Potential energy

Answer 9

is associated with an object that has the potential to move because of its position relative to some other location

Question 10

Gravitational potential energy

Answer 10

PE= mgh

Question 11

As an egg falls of a table, what are the energy conversions?

Answer 11

PE to KE

Question 12

Elastic potential energy depends on

Answer 12

distance compressed or stretched

Question 13

What is stored in a spring if an external force compresses or stretches it?

Answer 13

Elastic potential energy

Question 14

Elastic potential energy formula

Answer 14

PEelastic = 0.5k(x^2)

Question 15

When is k small? big?

Answer 15

Small if spring very flexible and big if spring is stiff

Question 16

At the highest point in its path, what type of energy does a pendulum have the highest of?

Answer 16

Gravitational potential energy

Question 17

At its lowest point, what type of energy does a pendulum have the most of?

Answer 17

Kinetic energy

Question 18

Mechanical energy

Answer 18

Sum of kinetic and all forms of potential energy

ME = KE + PE

Question 19

Conservation of mechanical energy

Answer 19

In the absence of friction, mechanical energy stays constant althouhg KE and PE can interconvert.

Question 20

Power

Answer 20

W/t or rate of energy transfer.

Question 21

What type of function is work?

Answer 21

A path function which means it depends on path taken

Question 22

When is work a state function? and why?

Answer 22

In a gravitational field, work is independent of the path taken because only force acting is gravity and therefore work will depend on vertical distance traveled.

Question 23

When an object is lifted to a certain height, what type of energy is the work equal to at that height?

Answer 23

Gravitational potential energy or W=mgh

Question 24

Work done against gravity is equal to

Answer 24

mgh

Question 25

If there is centripetal force and an object moves in a circular path, what is the work?

Answer 25

It is zero because displacement and force are perpendicular to eachother

Question 26

A student holds a 10kg stack of books 1.5m above the ground for 20s. How much power was used to hold the books during this time?

Answer 26

Power is given by P=W/t=F→⋅d→/t. Although the student exerts a force on the books during this time, they are not moved at all, so the displacement d is 0, and thus the power is also 0.