Question

a weight lifter lifts 150N of weight when doin curls. if he lifts the weight a distance of 40 cm in each curl (rep) how many reps must he make in 1.0 minute in order to reach a pwer of 25 watts? please explain why using
power=work/time
and
work=force x distance

Answer 1

power = work/time

150N / 60 seconds = 2.5 watts

25 / 2.5 = 10 reps

I think

Answer 2

haha thanks

Answer 3

dont forget to click good answer :p

Answer 4

sure :)

Answer 5

i don't think that's right, a newton is not a unit of work?

Answer 6

WHOOPSS 250N not 150 srry!!

Answer 7

do you know the formula to compute energy from work and distance?

Answer 8

sorry dont :(

Answer 9

which textbook are you using?

Answer 10

newton is not a unit of work what is?

Answer 11

a joule

Answer 12

work (in joules) = force (in newtons) times displacement (in meters)

Answer 13

im not using a text book my teacher just gave me a sheet with a bunch of problems

Answer 14

ok, you must have some reference though? something you're learning from? what did the teacher teach you from?

Answer 15

anyway, given the formula I just gave you can you compute the work done with each rep?

Answer 16

she just taught us
srry

Answer 17

ok thaanks

Answer 18

we haven't gotten through the problem yet

Answer 19

ok

Answer 20

the first step is to compute the work done with each rep

Answer 21

it's just force (in newtons) times distance (in meters)

Answer 22

150 * 0.4?

Answer 23

wouldnt it be 40?

Answer 24

yeah (except, it turns out the problem said 250 N, absolutezero mistyped it hte first time)

Answer 25

yeaa sorry

Answer 26

oops yes

Answer 27

ok absolute0 so what number do you get for joules per rep?

Answer 28

250 * 0.4 = 100 joules

Answer 29

right, now with 100 joules you can do the computation you started to do earlier -- 100 joules * x reps divided by 60 seconds = 25 watts

Answer 30

250 x 40 = 10000 is wat my calculator told me

Answer 31

wait how is it 0.4?

Answer 32

40 is centimeters, absolute0 - you have to make sure to do conversion to meters

Answer 33

ooooooo thank you

Answer 34

100 * 25 = 2500

2500 / 60 = 41 reps?

Answer 35

41.666667 or 42?

Answer 36

i get 15

Answer 37

100 joules / 60 seconds = 1.66667 watts doing 1 rep per 60 seconds

Answer 38

25/1.66667 = 15

Answer 39

google calculator is really useful here because it does dimensional analysis for you

Answer 40

https://www.google.com/#sclient=psy-ab&hl=en&site=&source=hp&q=(100+joules+%2F+unit)+*+(15+units%2Fminute)&pbx=1&oq=(100+joules+%2F+unit)+*+(15+units%2Fminute)&aq=f&aqi=&aql=1&gs_sm=e&gs_upl=667l667l0l1197l1l1l0l0l0l0l197l197l0.1l1l0&bav=on.2,or.r_gc.r_pw.r_cp.,cf.osb&fp=6017915d9066490&biw=1024&bih=667

Answer 41

actually this does the whole thing: http://tinyurl.com/7uhqkws

Answer 42

thank you!! i apreciate it ;)

Answer 43

no problem, and if i could ask, because i'm interested - are you in an online school, or a physical school?

Answer 44

im in a physical school why?

Answer 45

but they don't give you a textbook? how are you supposed to study at home?

Answer 46

well the teacher just showed us this on the white board and besides this was is an assignment

Answer 47

but where are you supposed to ge tthe formulas from and stuff?

Answer 48

the teacher taught us this using a video then further explaining it

Answer 49

but you don't have any written reference?

Answer 50

not that i know of sorry

Answer 51

interesting ...

Answer 52

well last year and this year we didnt do much textbook work