Question

A 10-kg tortoise sits on a see-saw 1 meter from the fulcrum. Where must a 2 - kg hare sit in order to maintain rotational equilibrium? Assume the see-saw is massless.

Answer 1

Given:

The mass of the tortoise is

$m_1=10\text{ kg}$

The mass of the hare is

$m_2=2\text{ kg}$

The position of the tortoise is

$r_1=1\text{ m}$

Required:

calculate the position of the hare

Explanation:

to calculate the position of the hare we will use the torque concept here that is given as

$T=rF$

here r is the position and F is force due

we know that F is force of gravity that is equal to the weight.

rotational equilibrium means that total torque on the system is zero.

then the above relation as

$r_1m_1g=r_2m_2g$

plugging all the values in the above , we get

$\begin{gathered} 10\text{ kg}\times1\text{ m}\times9.8\text{ m/s}^2=r_2\times2\text{ kg}\times9.8\text{ m/s}^{\placeholder{⬚}} \\ r_2=\frac{98}{2\times9.8} \\ r_2=5\text{ m} \end{gathered}$

Thus, the position of the hare is 5 m