Question

A 0.70-kg block is hung from and stretches a spring that is attached to the ceiling. A second block is attached to the fi rst one, and the amount that the spring stretches from its unstrained length triples. What is the mass of the second block?

Answer 1

1.4 kg

Step-by-step explanation:

m1 = 0.7 kg

Let the mass of second block is m.

x1 = x

x2 = 3x

According to the Hooke's law

F1 = - kx1

m1 g = - k x

0.7 g = - k x ..... (1)

When both the blocks are placed

(m1 + m2) g = - k x2

(0.7 + m) g = - 3 k x .... (2)

Divide equation (2) by equation (1), we get

(0.7 + m) / 0.7 = 3

0.7 + m = 2.1

m = 2.1 - 0.7

m = 1.4 kg

thus, the mass of second block is 1.4 kg.