Work and Machines

Question 1

work

Answer 1

a transfer of energy that occurs when a force makes an object move (force acting through a distance)

Question 2

for work to occur…

Answer 2

there must be a force causing an object to move in the direction of the applied force

Question 3

equations & units (work)

Answer 3

work = force x distance
force = work/distance
distance = work/force

work - joules (J)
force - newtons (N)
distance - meters (m)

Question 4

conditions for work

Answer 4

force, cause, displacement

Question 5

work and energy are related since…

Answer 5

energy is always transferred from the object doing the work to the object the work is done on

Question 6

power

Answer 6

the amount of work done in a certain amount of time; rate at which work is done

Question 7

equations & units (power)

Answer 7

power = work/time
work = power x time
time = work/power

power - watts (W)
work - newtons (N)
time - seconds (sec)

• energy can also substitute for work

Question 8

as force goes down…

Answer 8

distance goes up

Question 9

machine

Answer 9

a device that makes doing work easier

Question 10

what do machines do to make work easier?

Answer 10

they can change applied force and/or the direction of the applied force.

Question 11

the same amount of work can be done by…

Answer 11

using more force, less distance or using less force, more distance.

Question 12

machines help move things that…

Answer 12

resist being moved.

Question 13

input force/effort force

Answer 13

the force applied to the machine

Question 14

output force/resistance force

Answer 14

the force applied by the machine in order to overcome resistance

Question 15

the amount of energy transferred to an object from the machine cannot be…

Answer 15

greater than the amount of energy transferred to the machine.

Question 16

some energy is transferred into…

Answer 16

heat energy due to friction.

Question 17

an ideal machine with no friction would have…

Answer 17

the same work input and output.

Question 18

efficiency

Answer 18

the measure of how much work put into a machine is changed into useful output work by the machine.

Question 19

efficiency equation

Answer 19

work output/work input x 100 = __%

Question 20

the efficiency of a machine is always

Answer 20

less than 100%

Question 21

what can make a machine more efficient and how?

Answer 21

lubricants, reducing friction

Question 22

nemesis of work is…

Answer 22

friction.

Question 23

efficiency relates to the law of conservation of energy because

Answer 23

you can never get more work from a machine than what you put in.

Question 24

mechanical advantage

Answer 24

the amount of times a machine multiplies the input force (no unit)

Question 25

two types of mechanical advantage (equations)

Answer 25

AMA - force output/force input IMA - distance input/distance output

Question 26

how can you manipulate a lever to change MA

Answer 26

the longer the input arm, the greater the MA

Question 27

simple machine

Answer 27

machine the uses only one movement for work

Question 28

compound machine

Answer 28

machine that is a combination of two or more simple machines

Question 29

inclined plane

Answer 29

a sloping surface used to reduce force required for work

Question 30

lever

Answer 30

a bar that is free to pivet around a free point called a fulcrum

Question 31

first class lever

Answer 31

fulcrum is between input and output nothing is multiplied

Question 32

second class lever

Answer 32

output is between fulcrum and input MA > 1 multiplies force

Question 33

third class lever

Answer 33

input is between fulcrum and output MA < 1 distance is increased

Question 34

screw

Answer 34

an inclined plane wrapped around a cylindrical post

Question 35

wedge

Answer 35

an inclined plane with one or more sloping sides

Question 36

pulley (first class lever)

Answer 36

grooved wheel with a rope, simple chain, or cable running along the groove

Question 37

block and tackle system

Answer 37

a system of fixed and moveable pulleys

Question 38

inclined planes (ex.)

Answer 38

inclined plane, wedge, screw

Question 39

pulleys (ex.)

Answer 39

wheel & axel, pulley, lever

Question 40

fixed pulley

Answer 40

attached to something that doesn't move, force isn't multiplied but the direction is changed, IMA & AMA of 1

Question 41

moveable pulley

Answer 41

MA of 2, multiplies force, one end of the string is fixed but the wheel is free to move