Mechanics III

Question 1

what is the unit for work, W?

Answer 1

N*m=J

Question 2

what component of force does work?

Answer 2

the component of force that acts in the same direction of displacement d

Question 3

is work a vector or scalar?

Answer 3

it is a scalar value

Question 4

what can the sign of work be or indicate?

Answer 4

positive work: work done by environment on object causing gain in kinetic energy, zero work: force acts perpendicular, negative work: work done by object on environment causing loss of kinetic energy

Question 5

power

Answer 5

measures how fast work gets done

Question 6

what is the unit for power?

Answer 6

J/s=W (watt)

Question 7

energy

Answer 7

the ability to do work

Question 8

kinetic energy

Answer 8

the energy of an object due to motion

Question 9

is energy a vector or scalar?

Answer 9

energy is a scalar value

Question 10

work-energy theorem

Answer 10

total work done on the object is equal to the change in its kinetic energy

Question 11

potential energy

Answer 11

energy an object has by virtue of its position

Question 12

change in gravitational potential energy is the opposite:

Answer 12

of the work done by the gravitational energy

Question 13

what does a positive change in potential energy mean?

Answer 13

increased height of object

Question 14

what does a negative change in potential energy mean?

Answer 14

decreased height of object

Question 15

is potential energy absolute?

Answer 15

no, it is a relative quantity. it is the changes in potential energy that are important and physically meaningful

Question 16

conservative force

Answer 16

independent of the path an object follows

Question 17

what is an example of a conservative force?

Answer 17

gravity

Question 18

nonconservative force

Answer 18

does depend on the path taken

Question 19

what is an example of a nonconservative force?

Answer 19

friction

Question 20

potential energy can only be defined for:

Answer 20

conservative forces

Question 21

total mechanic energy, E

Answer 21

the sum of the object’s kinetic and potential energy

Question 22

Conservation of Total Mechanical Energy

Answer 22

If the only forces acting on an object during its motion are conservative (no friction), then the object’s mechanical energy will remain the same throughout the motion

Question 23

what happens if friction acts during an object’s motion?

Answer 23

the total mechanical energy is not conserved

Question 24

mechanical advantage

Answer 24

quantity that describes how much less force is required when using that particular simple machine

Question 25

how to calculate mechanical advantage (MA)?

Answer 25

resistance force/effort force=F without machine/F with machine=F out/F in

Question 26

resistance force

Answer 26

the force that would be applied if no machine were being used

Question 27

effort force

Answer 27

the force applied with the use of the machine

Question 28

efficiency

Answer 28

measures the degree to which friction and other factors reduce the actual work output of the machine from its theoretical maximum

Question 29

how to calculate percentage efficiency

Answer 29

W output/Energy input

Question 30

how does an efficiency of less than 100% affect mechanical advantage?

Answer 30

the mechanical advantage will decrease

Question 31

momentum, p

Answer 31

the product of mass and velocity, a vector

Question 32

impulse

Answer 32

the change in moment, force applied for an interval of time

Question 33

Law of Conservation of Momentum

Answer 33

in a system of interacting objects with no NET external force, then to total momentum of the system will remain constant and be conserved

Question 34

p=mv and the Law of Conservation of Momentum is also known as:

Answer 34

linear momentum or the Law of Conservation of Linear Momentum

Question 35

elastic collision

Answer 35

total momentum AND total kinetic energy are conserved

Question 36

inelastic collision

Answer 36

total momentum is conserved but total kinetic energy is not

Question 37

perfectly inelastic collision

Answer 37

an inelastic collision in which the objects stick together afterwards

Question 38

angular momentum, L

Answer 38

must be defined relative to some reference point, =lmv, Iw (moment of inertia times angular velocity)

Question 39

what is required for a greater desired change in momentum?

Answer 39

either a stronger applied force or a longer time interval in which the force is applied

Question 40

force is also the rate of change of:

Answer 40

linear momentum p

Question 41

torque is also the rate of change of:

Answer 41

angular momentum L