Question

A seesaw made of a plank of mass 10.0 kg and length 3.00 m is balanced on a fulcrum 1.00 m from one end of the plank. A 20.0-kg mass rests on the end of the plank nearest the fulcrum. What mass must be on the other end if the plank remains balanced?

Answer 1

The mass at the other end is 7.5 kg.

Step-by-step explanation:

Let the mass is m.

Take the moments about the fulcrum.

20 x 1 = 10 x 0.5 + m x 2

20 = 5 + 2 m

2 m = 15

m = 7.5 kg

Answer 2

7.5 kg

Step-by-step explanation:

We are given that

`m_1=10 kg`

Length of plank, l=3 m

Distance of fulcrum from one end of the plank=1 m

`m_2=20 kg`

We have to find the mass must be on the other end if the plank remains balanced.

Let m be the mass must be on the other end if the plank remains balanced.

In balance condition

`20* 1=10* (1.5-1)+m* (1.5+0.5)`

`20=10(0.5)+2m`

`20=5+2m`

`2m=20-5=15`

`\implies m=(15)/(2)`

`m=7.5 kg`

Hence, mass 7.5 kg must be on the other end if the plank remains balanced.