Use the worked example above to help you solve this problem. A woman of mass m =

Question

Use the worked example above to help you solve this problem. A woman of mass m = 51.0 kg sits on the left end of a seesaw—a plank of length L = 3.94 m—pivoted in the middle as shown in the figure.

(a) First compute the torques on the seesaw about an axis that passes through the pivot point. Where should a man of mass M = 67.6 kg sit if the system (seesaw plus man and woman) is to be balanced?
2. m

(b) Find the normal force exerted by the pivot if the plank has a mass of mpl = 10.0 kg.
3. N

(c) Repeat part (a), but this time compute the torques about an axis through the left end of the plank.
4. m

----EXERCISE HINTS: GETTING STARTED!!!! (NEED ANSWERS :) :))
Suppose a 34.2 kg child sits 1.10 m to the left of center on the same seesaw as the problem you just solved. A second child sits at the end on the opposite side, and the system is balanced.

(a) Find the mass of the second child.
mass child 2 = kg

(b) Find the normal force acting at the pivot point.
Fn = N

Explanation / Answer

Suppose a 34.2 kg child sits 1.10 m to the left of center on the same seesaw as the problem you just solved. A second child sits at the end on the opposite side, and the system is balanced.

(a) Find the mass of the second child.
mass child 2 = kg

(b) Find the normal force acting at the pivot point.
Fn = N

Torque about axis, T = Force, F x Perpendicular distance, R

Taking anti-clockwise torque to be positive
Torque due to first child, T1 = (34.2 x g) x 1.10
Torque due to second child, T2 = -(M2 x g) x (L/2)

When see-saw is balanced, T1 + T2 = 0

Therefore,

(34.2g)x1.10 - (M2g)x(L/2) = 0

Sub in values of g and L to solve.

For b,

Summation of y forces: (M1 + M2)g +(Mass of plank x g) =Fn

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