Question

A barbell is 1.5 m long. Three weights, each of mass 20 kg, are hung on the left and two weights of the same mass, on the right. The width of each weight is 4 cm and each group of weights is placed 4 cm from the ends. Where is the center of mass of the barbell as measured from the mid-point, M, of the bar? The bar is of uniform mass and has mass 5 kg, and the retaining collars are of negligible mass. Take to the right as positive.

Answer 1

Answer:

r = -11.6 cm

Explanation:

As we know that the position of center of mass is given as

$r = \frac{m_1x_1 + m_2x_2 + .................}{m_1 + m_2 + m_3..............}$

now we know that three masses are on the left while two are on the right

position of left most mass with respect to the center of the rod is given as

$x_1 = -69 cm$

$x_2 = -65 cm$

$x_3 = -61 cm$

$x_4 = + 69 cm$

$x_5 = +65 cm$

Now we will have

$r = \frac{20(-69) + 20(-65) + 20(-61) + 20(+69) + 20(+65) + 5(0)}{105}$

$r = -11.6 cm$