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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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Answer:

The answer to this question is given below in this explanation section.

Explanation:

                     " law of conservation of energy"

The law of conservation of energy states that energy can neither be created nor destroyed only converted from one form of energy into another.This mean that a system always has a same account of a energy,unless it is added from the outside.This is particularly confusing in the case of non conversation forces,where energy is converted from ,mechanical energy into thermal energy.but the overall energy does remain the same.The only way to use energy is to transform energy from one form to another.

The amount of energy in any system than it is determined by the following equation.

Ut=Ui +W+Q

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It is also possible to determined the change in internal energy of the system using the equation.

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The mechanical energy of a system increases provided their is no loss of energy due to friction.The energy would transform to kinetic energy when the speed is increasing.Te mechanical energy of a system remain constant provided their is no loss of energy due to friction.

The law of conversation of energy which say that in a closed system total energy is conserved that is it constant.

KE1 + PE1=KE2+PE2

 

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