Question

PLEASE HELP!!!!!!! MT TIME FOR MY TEST IS ALMOST OVER!!!

An ideal spring, with a pointer attached to its end, hangs next to a scale. With a 100-N weight attached, the pointer indicates "40" on the scale as shown. Using a 200-N weight instead results in "60" on the scale. Using an unknown weight X instead results in "30" on the scale. The weight of X is:

Answer 1

50 N

Step-by-step explanation:

Let the natural length of the spring = L

so

100 = k(40 - L) (1)

200 = k(60 - L) (2)

(2)/(1): 2 = (60 - L)/(40 - L)

60 - L = 2(40 - L)

60 - L = 80 - 2L

2L - L = 80 - 60

L = 20

Sub it into (1):

100 = k(40 - 20) = 20k

k = 100/20 = 5 N/in

Now

X = k(30 - L) = 5(30 - 20) = 50 N