Force Strings for Junior High School Grade 7

strings in force

1. Springs & Strings

2. Springs
Spring Force
A stretched or compressed spring exerts one of the most common
contact forces. A spring can either push (when compressed) or pull
(when stretched).
In either case, the tail of the vector force is attached to the contact
point.
There is no special symbol for the spring force, but we can use F
sp.

3. Hooke’s law for springs states that the force
increases linearly with the amount the spring is
stretched or compressed:
k spring constant
units N/m
F kx
Hooke’s Law Springs

4. Hooke’s law for springs states that the force increases linearly with the
amount the spring is stretched or compressed. The force is negative
because it always opposes the compression or extension of the spring.
F kx
Hooke’s Law Springs

5. 27•• IP The equilibrium length of a certain spring with a force constant
of k = 250 N/m is 0.18 m. (a) What force is required to stretch this
spring to twice its equilibrium length? (b) Is the force required to
compress the spring to half its length the same as in part (a)? Explain.
0.18 m
F = -k x
x = 0.18 m
F = -(250 N/m)(0.18 m)
F = -45 N
(a)
(b)x = - 0.09 m
F = -(250 N/m)(- 0.09 m)
F = 22.5 N