physics 10.2

distinguish between theoretical mechanical advantage and actual mechanical advantage how would these compare if a machine were 100% efficient

theoretical mechanical advantage assumes no friction and actual mechanical advantage considers the effects friction has if a machine were 100% efficient, they would be equal

what class of lever is the fulcrum in the middle what class of lever is the force in the middle what class of lever is the weight in the middle

type 1 type 3 type 2

in which type of lever is the output force always smaller than the input force

type 3

calculate the work needed to lift a 90 N block of ice a vertical distance of 3.0 m when the same block of ice is raised the same vertical distance by pushing it up a 5.0 m long ramp, only 64.0 N of force is required. calculate the work done to push the block up the ramp what pe does the block have is the ramp ideal or not

w = 90(3) = 270 J w = 64(5) = 320 J pe = (9.2)(9.8)(3) = 270 J no, the useful work out is less than the work in (friction)

in what ways is a machine subject to the law of conservation of energy is it possible for a machine to multiply energy or work

wort out cannot exceed work in it is not possible to multiply energy or work

a bus steering wheel has a diameter of 50.8 cm. it turns the steering wheel column, which has a diameter of 7.6 cm. if the driver applies 22.3 N of force to turn the wheel, how much force does the steering column exert to steer the bus

.508(22.3) = .076f f = 149 N

peter used a stick 1.8 meters long to push aside a large rock in the yard. the fulcrum was 0.3 meters from the resistance. what is the ideal mechanical advantage of the stick

1.8 / 0.3 = 6

the weight of a delivered package and its contents is 500 N. if a crowbar has a mechanical advantage of 10, what effort force is needed to lift the box with the crowbar so a cart could be slide underneath the box

10 = 500 / f f = 50 N

what is the efficiency of her body when a cyclist expends 1000 W of power to deliver mechanical energy to the bicycle at the rate of 100 W

100/1000 = 10%

what is the efficiency of a machine that requires 100. J to do 35 J of useful work

35/100 = 35%

what is the ideal mechanical advantage of an inclined plane that is 40 meters long and 8 meters high

40/8 = 5

karen was helping her father repair the roof of their house. they needed to bring a variety of tools and materials to the roof. karen suggested constructing a pulley. the heaviest load weighed 400 N. karen wanted to exert a max force of 100 N. how many strings between the wheels should karen's pulley have

400/100 = 4 strings

a lever is used to lift a heavy load. when a 50 N force pushes one end of the lever down 1.2 meters, the load rises 0.2 meters. calculate the weight of the load. neglect friction

50*1.2 = .2f f = 300 N

in raising a 5000 N piano with a pulley system, the workers note that for every 2 m of rope pulled down, the piano raises 0.4 m. ideally, how much force is required to lift the piano if the workers actually pull with 2500 N of force, what is the efficiency of the pulley system

5000 * .4 = 2f f = 1000 N 5000(.4) / 2(2500) = 40%

the head of the bolt is 2.54 cm above the surface of the metal. the bolt is then turned 10 complete times. the head of the bolt is now 1.90 cm from the surface of the metal. the diameter of the bolt is 1.10 cm. what is the ideal mechanical advantage of the bolt

?????

why does a small, lightweight car generally have better fuel economy than a big, heavy car how does a streamlined design improve fuel economy

a small mass means less kinetic energy is needed for the same amount of speed reduces air resistance and friction

in what two ways can a machine alter an input force

can change a force's magnitude and/or direction

what does it mean to say that a machine has a certain mechanical advantage

the machine can multiply the force by a certain amount

what happens to a person whose combined work and heat output is less than the energy consumed what happens when the person's work and heat output is greater than the energy consumed

the person will gain weight the person will lose weight