Question

A gymnast is hanging from the parallel bars and swinging around the bar. If the length of the gymnast is 1.98 meters and the gymnast has a rotational inertia of 85.0 kg·m^2, what is the mass of the gymnast?

21.7 kg

43.4 kg

85.0 kg

65.0 kg

Answer 1

@518nad

Answer 2

We can assume she's like a rod spun around one end - so look in your notes or w/e or google and find the equation for rotational inertia for that.

Answer 3

i=mr^2

Answer 4

http://hyperphysics.phy-astr.gsu.edu/hbase/imgmec/mic.gif

Answer 5

ph would it be the 1/3 or 1/12 one?

Answer 6

See my first post.

Answer 7

ok so 1/3 ml^2

Answer 8

85= m 1.98^2
85= 3.9204m
m=21.7kg

Answer 9

have u learnt integration?

Answer 10

no

Answer 11

Why did you quote the correct formula, and then not even use it in your very next post?

Answer 12

Do you think 21.7kg seems reasonable for a gymnast? That's about 45 pounds.

Answer 13

oh my bad i completely forgot about the 1/3

Answer 14

ok i put the 1/3 in and got 65.0kg

Answer 15

@agent0smith

Answer 16

Does it seem reasonable?

Answer 17

143 pounds yeah i guess

Answer 18

@agent0smith

Answer 19

It seems reasonable.

Answer 20

ok thank you If you increase the radius of a ring by a factor of four, you increase the rotational inertia by a factor of sixteen.

True

False
would this be false?

Answer 21

@agent0smith

Answer 22

Look at the equation for rotational inertia. What happens if you quadruple the radius?

Answer 23

you would square it so it would be true

Answer 24

@agent0smith

Answer 25

Yep.

Answer 26

thanks!