how do u find the mass of this block?

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 first one, and the amount that the spring stretches from its unstrained length triples. What is the mass of the second block?

Answer 1

set up two equations using the general equation for a spring:
F=k*x

For the first case
.7*g=k*x
for the second
(.7+m)*g=k*3*x

(.7+m)*g/3=.7*g
.7+m=.7*3
m=.7*2
=1.4

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Answer 2

If you draw a free body diagram (FBD) of what's going on here, you'll have gravity pulling down 0.70 kg * g (gravity) and an equivalent force pulling up, F1.
The equation for the force in a spring is F=k*x, where k is a constant and x is the stretched legnth of the spring. So, in your case: F1=k*x1 = 0.70 * g
in the next case, the length is trippled, so:
F2=k*3*x1
k*3*x1=(0.70 + m2)*g
where m2 is the new mass
You should be able to take it from there :)

Answer 3

The mass of the second block must be 1.4Kg, as the total mass is then tripled, assuming the spring is linear in its stretching.

Answer 4

Block stretches spring....x distance

second block stretches spring.....3 times unrestrained...

info is incomplete but I think the spring has stretched the same amount each time so blocks are the same.....but only if the spring is linear in its properties...

Answer 5

If X is proportional to Y, then

X1/X2 = Y1/Y2.

In the case of spring,
Length is proportional to the force or mass, since g is the same for both.

M2 /M1 = L2/L1 = 3 (given).

M2 = 3*0.7 = 2.1

The mass added is 2.1 - 0.7 = 1.4 kg.