How High Does a Jumper Raise Their Center of Gravity?

[bionut]

Homework Statement

A jumper takes off with a velocity of 5 ms at an angle of 20 degrees to the horizontal.
How high does he raise his center of gravity?

Homework Equations

The Attempt at a Solution

I know that Vh= 5scos20 = 1.7 m/s and Vv=5Csin20=4.70 m/s

using 0=Vi^2 + 2ad
0=5sin20 + 2 X-9.81d
19.62d=1.7
d=1.7/19.62
d=0.087m, but its incorrect. Am I misssing something? The only Thing I can think of is beacuse its his centre of gravity that I should treat it as a vertical launnched projectile?

 

[PeterO]

Homework Statement

A jumper takes off with a velocity of 5 ms at an angle of 20 degrees to the horizontal.
How high does he raise his center of gravity?

Homework Equations

The Attempt at a Solution

I know that Vh= 5sin20 = 1.7 m/s and Vv=5Cos20=4.70 m/s

using 0=Vi^2 + 2ad
0=5sin20 + 2 X-9.81d
19.62d=1.7
d=1.7/19.62
d=0.087m, but its incorrect. Am I misssing something? The only Thing I can think of is beacuse its his centre of gravity that I should treat it as a vertical launnched projectile?

Nothing wrong with your calculation. Since they are asking how high, could this be the high-jump and the angle is actually 20 degrees to the vertical?

 

[bionut]

thanks for your help, that's what i was thinking would it then mean that the Vv is 5Cos20 instead of 5Sin20? Is that what you are suggesting?, also the answer is 0.14m...

 

[bionut]

Can anyone else help... I still can't get 0.14m?

:-(