Lecture 2

Question 1

Torque

Answer 1

Measure of a forces ability to cause acceleration

acting on a point besides center of mass

greater torque means greater rotational acceleration

Question 2

What increases Torque

Answer 2

Force acting perpendicular

distance between point of application and point of rotation

T=Fl

(length lever)

Question 3

Static equilibrium

Answer 3

velocities are zero

Question 4

Equilibrium

Answer 4

no net force, no net torque. May be moving, but not accelerating

Question 5

dynamic equilibrium

Answer 5

any velocities are non zero, but are constant - all forces balanced

Question 6

Systems not in equilibrium

Answer 6

Center of mass accelerating translationally or other parts accelerating rotationally

sum of forces= MA

OR

F upward= F downward

ADD Ma to the side with less force

Question 7

Open system

Answer 7

can exchange energy and mass with surroundings

Question 8

closed system

Answer 8

exchange of energy- not mass- with surroundings

Question 9

isolated system

Answer 9

no exchange of energy or mass with surroundings

Question 10

Joule

Answer 10

1 J= 1 kg m^2 / s^2= 1 Nm

Question 11

Mechanical energy

Answer 11

energy of a macroscopic system

Me= KE + UE

Question 12

Kinetic energy

Answer 12

energy of motion

K= 1/2 mv^2

Question 13

Types of potential energy

Answer 13

gravitational, elastic

Question 14

Elastic potential energy

Answer 14

restorative elastic

Ue= 1/2 K X^2

Question 15

Gravitational potential energy

Answer 15

Ug= mgh

Question 16

Heat

Answer 16

energy transferred between a system and its surroundings due to temperature difference

Question 17

Work

Answer 17

energy transferred for any other reason than temperature difference

equals change of energy

Question 18

First law of thermodynamics

Answer 18

Any change in total energy of a system is due to work or heat

Energy is conserved

W + q= delta E total

W + q= Delta K + delta U

Question 19

work energy theorem

Answer 19

W= delta K

energy transfer leads to change in kinetic energy

when work is done, energy changes

Question 20

work equation

Answer 20

W= fdcos theta= delta K + delta U

Question 21

When does energy go into a system

Answer 21

when work is done on it

Work is positive

Question 22

When does energy go out of a system

Answer 22

when the system does work

work is negative

system transfers energy to surroundings which decreases its own energy

Question 23

Power

Answer 23

rate of energy transfer

P= W/t or delta E/t

in watts or J/s

Question 24

conservative force

Answer 24

when it does work on a system, the system experiences no change in mechanical energy

total work= zerp

Question 25

law of conservation of mechanical energy

Answer 25

only when conservative forces are acting, the sum of mechanical energies remains constant

Hookes and gravity

Question 26

conservation of mechanical energy equations

Answer 26

K1 U1 = K2 U2

0= delta U + delta K

Question 27

How much work is done by gravity?

Answer 27

gravity is conservative, not part of the system

use FDcos theta

dont include GPE in delta U

Question 28

non conservative forces

Answer 28

withdraw energy from a system

change total amount (mechanical energy)

W= delta K + delta U

Question 29

mechanical advantage

Answer 29

reduce applied force using a machine

lever, ramp, pulley