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inna [77]
3 years ago
7

Two kids create a makeshift seesaw by setting a 4-m long uniform plank on a saw horse. The saw horse is 0.5 m to the left of the

center of mass of the plank. The child of mass m1 = 42 kg sits at the left end of the plank. The child of mass m2 = 31 kg sits 1 m to the right of the center of mass of the plank. What is the mass of the plank?
Physics
1 answer:
GREYUIT [131]3 years ago
3 0

Answer:

The mass of the plank is 33 kg.

Explanation:

Given that,

Length of plank = 4 m

Distance in left from the center= 0.5 m

Mass of child = 42 kg

Mass of other child = 31 kg

Distance in right from the center= 1 m

We can sum torques around the saw horse; each force generates a torque equal to force x distance from saw horse

We need to calculate the torque for first child

Using formula of torque

\tau =mg\times d

Put the value into the formula

\tau=42\times9.8\times1.5

\tau=617.4\ N-m

We need to calculate the torque for second child

The child is 1.5 m from the saw horse

Using formula of torque

\tau' =mg\times d

Put the value into the formula

\tau'=31\times9.8\times1.5

\tau'=455.7\ N-m

The weight of the plank produces a clockwise torque

\tau''=mg\times d

\tau''=mg\times 0.5

We need to calculate the mass of the plank

Using balance equation of torque

\tau=\tau''+\tau'

Put the value into the formula

617.4=mg\times0.5+455.7

m=\dfrac{617.4-455.7}{0.5\times9.8}

m=33\ kg

Hence, The mass of the plank is 33 kg.

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