Unit 7 - Work and Energy

Question 1

ENERGY __>

Answer 1

Measure of ability to do ork
Never destroyed
Only ever transformed from one form to another

Question 2

One Joule is

Answer 2

When one N of force is applied to move an object throguh 1m

Question 3

What is one calorie

Answer 3

The ammount of energy required to raise 1 kg of water by 1 deg

Question 4

W=

Answer 4

Fd

Question 5

Only the component of force that lies __________ to the dispalcement does work

Answer 5

Parallel

Question 6

Rewrite the equation for Fh

Answer 6

W = Fxcos theta

Question 7

Kinetic energy is

Answer 7

The energy an object has due to motion which depends on the mass and speed of the object

Question 8

Ke =

Answer 8

1/2 mv^2

Question 9

Ke is always

Answer 9

Positive

Due to v^2 being positive or 0

Question 10

Delta Ke =

Answer 10

W net

Question 11

Ke is a ________ quantity

Answer 11

scalar

Question 12

GPE is

Answer 12

Potential an object has to do work as a result of being located at a particualr position in a gravitational feield

Question 13

GPE =

Answer 13

mgh

Question 14

What happens if you remove the force holding the object up

Answer 14

GPE converted to Ke of the falling object

Question 15

Energy (E) =

Answer 15

Power X time

Question 16

Give the 2 laws of newtons laws of gravitation

Answer 16

F = gm1m2 / r^2

GPE = -Gm1m2 / r

Question 17

In mechanics what fundamental quantities are conserved

Answer 17

Energy, momentum and angular momentum

Question 18

Total energy in an isolated system always

Answer 18

Remains the same

Question 19

What is the equation that shows conservation of energy in an isolated system

Define the terms

Answer 19

Eki + Ugi + Usi = Ekf + Ugf + Usf + Ehf

Ek - kinetic
Ug - GPE
Us - elastic string potential
Eh = heat

i - initial
f - final

Question 20

summarise the equation stating conservation of energy in an isolated system

Answer 20

Potential/inital energy = final energy

Question 21

Define thermal energy

Answer 21

Energy contained within a system responsible for its temperature

Question 22

Heat is the

Answer 22

Flow of thermal energy

Question 23

Equation for change in thermal energy

Define the terms

Answer 23

Uk . Fn . d

Uk - coefficient of kinetic friction
Fn - normal force
d - distance

Question 24

What type of friction generates heat, which type doesnt

Answer 24

Force a static friction

Force of kinetic friction

Question 25

1W =

Answer 25

1 J per second

Question 26

Power is

Answer 26

The rate at which work is done

Question 27

3 equations for power

Answer 27

P = delta E / delta t P = Fv P = mav

Question 28

What is stress

Answer 28

force applied per unit of area

Question 29

What is strain

Answer 29

Extent of streching/compression produced as the material responds to stress is called the strain

Question 30

Equation of strain

Answer 30

Change in L / Original length

Question 31

What are the two types of deformation

Answer 31

Elastic and plastic

Question 32

Elastic

Answer 32

When stress removed it returns to original dimension REVERSIBLE AND NON PERMANENT

Question 33

Plastic

Answer 33

Stress is so large that when removed it does not return to its orignal dimensions IRREVERSIBLE AND PERMANENT

Question 34

Hookels law is the

Answer 34

Force required to strech an elastic object such as a metal spring is directly proportional to the extension of the spring

Question 35

F (Hookes Law0 =

Answer 35

- kx

Question 36

Why must you take care when calculating the length of a spring

Answer 36

substracting the nominal (resting) length

Question 37

Youngs Modulus -->

Answer 37

Elastic modulus measures the resistance of a material to be elastically deformed

Question 38

The stiffer the material the ________ the Young's modulus

Answer 38

Higher

Question 39

Young's Modulus =

Answer 39

Stress/Strain

Question 40

How can you obtain k from Youngs Modulus

Answer 40

K = EA/L ``` E = youngs modulus A = area L = length ```

Question 41

Spring constant when k in serioes

Answer 41

k/2

Question 42

Spring constant when k in parallel

Answer 42

2k

Question 43

What is elastic potential energy

Answer 43

EPE is energy tored as a result of applying force to deform an elastic object

Question 44

EPE =

Answer 44

1/2.k.(delta x)^2

Question 45

What are the two patterns energy follows

Answer 45

1/2 ab^2 abc