A vaulter holds a 34.1 N pole in equilibrium by exerting an upward force U with her leading hand and a downward force D with her trailing hand. Point C is the center of gravity of the pole. Given d1 = 1.100 m, d2 = 1.65 m, and d3 = 2.75 m, what are the magnitudes of U and D?
i am not sure of what formula to use for mag, pls help!!
3 answers
A figure or better description is needed to explain the orientation of the pole and the meaning of d1, d2, and d3.
It sounds like you are describing the situation in which the vaulter is running towards the bar while holding the pole horizontal. The trailing hand holds the bar near one end, pushing down, while the leading hand, about 2 meters ahead, pushes up.
What you need to do is write a moment equilibrium equation (total moment = 0) , with the weight of the pole acting at the center of gravity. Take moments about the location of one hand and you can solve directly for the force on the other hand.
2.75 m sounds short for a pole vaulter's pole, except perhaps for beginners. 3.5 meters is more typical
http://www.everythingtrackandfield.com/mfpbCat1PlusLanding.aspx_Q_CategoryID_E_194
What you need to do is write a moment equilibrium equation (total moment = 0) , with the weight of the pole acting at the center of gravity. Take moments about the location of one hand and you can solve directly for the force on the other hand.
2.75 m sounds short for a pole vaulter's pole, except perhaps for beginners. 3.5 meters is more typical
http://www.everythingtrackandfield.com/mfpbCat1PlusLanding.aspx_Q_CategoryID_E_194
sum of M_A=0
U(d_1)-F_y(d_1+d_2)=0
F_y=34.1 N
solve for U and plug in numbers.
sum of F_y=0
-D+U-F_y=0
solve for D, plug in numbers
U(d_1)-F_y(d_1+d_2)=0
F_y=34.1 N
solve for U and plug in numbers.
sum of F_y=0
-D+U-F_y=0
solve for D, plug in numbers