Spring constant problem?

Question

A person who weighs 740 N steps onto a spring scale in the bathroom, and the spring compresses by 0.69 cm.
(a) What is the spring constant?

I don't know..I tried k=740/.69, but this was incorrect.

(b) What is the weight of another person who compresses the spring by 0.29 cm?

This one I got. I set .69/.29=740x and got 311N which was correct. I don't know why I can't get the first part, but I would really appreciate anyone who would help me out! :)

Answer 1

You are correct
F=kx
so k=F/x
k= 740/ 0.0069=107250 N/m ( I think they wanted in N/m )

b) regardless of what k is

W1/x1=W2/x2 so

W2=W1(x2/x1)= 740 (.29/.69)
W2=311 N (you are correct again and we are in violent agreement)

Next time make sure you are using units consistently

Have fun.

Answer 2

Spring Constant Problem

Answer 3

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RE:
Spring constant problem?
A person who weighs 740 N steps onto a spring scale in the bathroom, and the spring compresses by 0.69 cm.
(a) What is the spring constant?

I don't know..I tried k=740/.69, but this was incorrect.

(b) What is the weight of another person who compresses the spring by 0.29 cm?

This...

Answer 4

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Let the spring is compressed by x meter,By the law of energy conservation:- =>PE(block) = PE(spring) =>mg(h+x) = 1/2kx^2 =>2 x 9.8 x (0.7+x) = 1/2 x 1960 x (x^2) =>980x^2 - 19.6x - 13.72 = 0 =>x = [-(-19.6)+/-√{(-19.6)^2 - 4 x 980 x (-13.72)}]/[2 x 980] =>x = [19.6 +/- 232.74]/1960 =>x = 0.1287 m =>x = 12.87 cm

Answer 5

They probably want k in terms of N/m not N/cm. Is your k off by a factor of 100? You are using the right formula. I think you just need to use meters instead of centimeters.