Two children, with masses 35 kg (on the left) and 41 kg (on the right), sit at o

Question

Two children, with masses 35 kg (on the left) and 41 kg (on the right), sit at opposite ends of a 3.5 m long seesaw with mass 23 kg , with the fulcrum at its midpoint.
Part A With the seesaw horizontal, find the net torque on the seesaw. Express your answer to two significant figures and include the appropriate units. Assume the counterclockwise rotation as positive.
Part B. With the seesaw horizontal, find its angular acceleration.Express your answer to two significant figures and include the appropriate units. Assume the counterclockwise rotation as positive.

Explanation / Answer

here,

mass of the right children , mr = 41 kg

mass of the left children , ml = 35 kg

length of sea saw , l = 3.5 m

A)

the net torque on the seesaw, T = - mr * l/2* g + ml * l/2 * g

T = 6 * 9.8 * 3.5 /2

T = - 102.9 N.m

the net torque on the sea saw is - 102.9 N.m

B)

the moment of inertia of the sea saw , I = mr * (l/2)^2 + ml * ( l/2)^2 + ms * l^2 /12

I = (3.5/2)^2 * ( 41 + 35) + 23 * 3.5^2 /12

I = 256.23 kg.m^2

torque = I * alpha

- 102.9 = 256.23 * alpha

alpha = - 0.4 rad/s^2

the angular accelration is - 0.4 rad/s^2

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