Question

A 73kg man weighs himself at the north pole and at the equator.. How much difference in weight is there, in Newtons?

Answer 1

You need to know the distance from the center of the earth to the north pole, and center of the earth to the equator. Then use:

\[\Large F = G \frac{ m M }{ r^2 }\]M is the earth's mass, m is the man's mass. r is the distance.

Answer 2

ok let me try that, one minute please

Answer 3

would i also use the different gravity readings as well ?

Answer 4

What different gravity readings? That formula should account for them.

Answer 5

its a difference of .03% between the two according to the net. but regardless I calculated 72.55 newtons. i entered the answer and it was not right. can you help.

Answer 6

How much difference in weight is there, in Newtons?

the difference was 0.03%? Then how'd you get 72.55 newtons? Show your work...

Answer 7

i know it doesn't make sense. G=6.67x10^-11 correct?

Answer 8

Correct. What values did you use for the two distances?

Answer 9

earth = 6751 km
equator = 6378

Answer 10

converted to meters i just added 3 zeros

Answer 11

this is how i set it up. (6.67X10^-11)*73*(5.972x10^24)/(4.53x10^13)

Answer 12

first: http://www.wolframalpha.com/input/?i=6.67*10%5E-11+*+5.97E24+*+73+%2F+6751000%5E2

second: http://www.wolframalpha.com/input/?i=6.67*10%5E-11+*+5.97E24+*+73+%2F+6378000%5E2

Answer 13

answer i got was 641.90

Answer 14

That looks off.

Answer 15

The Earth's equatorial radius a, or semi-major axis, is the distance from its center to the equator and equals 6,378.1370 kilometers
.
Polar radius
The Earth's polar radius b, or semi-minor axis, is the distance from its center to the North and South Poles, and equals 6,356.7523 kilometers

These numbers are hugely different from your two
earth = 6751 km
equator = 6378

Answer 16

yea thus why my calculations were wrong. the answer ended up being 2.5 newtons. i just don't see how though

Answer 17

Maybe you used the wrong radii?
http://www.wolframalpha.com/input/?i=6.67*10%5E-11+*+5.97E24+*+73+%2F+6378137%5E2


http://www.wolframalpha.com/input/?i=6.67*10%5E-11+*+5.97E24+*+73+%2F+6356752%5E2

Answer 18

That's about 5 newtons... but it'll depend on the exact numbers you used for the radii. I imagine they gave the radii to you...

Answer 19

Plus it depends what mass of earth you used....

Answer 20

due to axial rotation of earth there is a slight decrease in g=earth's gravity in equator,and g=maximum at pole.we can go by this equation.\[g'(observed)=g-R \omega^2\cos ^2\theta \]
at equator,\[\theta\]=0',at pole \[\theta \]=90'
so at equator a man weighs=mg'=m(g-w^2R)=73X(9.8-.00192)=715N
but at pole.9.8X73N=715.4N.

the difference will be .4 N.

hope this helps.

Answer 21

^the difference due to the radius of earth is much greater, though.