Apologia Physics: Hooke's Law

Hooke's Law refers to the relationship between the force applied to a spring and the distance it stretches.  F = -k . x where F is the force, k is the relationship factor, and x is the distance.  k is negative to indicate that the spring pulls back in the opposite direction after it is pulled.  The force which pulls the spring back to its original position is call the restorative force.  A strong spring has a high k and a weak spring, the opposite.

To demonstrate Hooke's Law we set up a simple apparatus.  We attached a ruler to the end of a work table.  There must be a hole in the end of the ruler.  We used a paper clip to attach a spring to the ruler and let the spring hang straight down toward the floor.  We then attached different weights, we used coins, to the end of the spring and measured how far the spring stretched.  Plot the points with the weight on the y axis and the distance on the x axis as the UOM for k is Newtons/meter.  Fit a straight line to the data points.  The line should fit the data reasonably well as k should be linear.  We used weights of 300, 500, and 800 grams.  Be sure to use a spring that will stretch and rebound with the range of weights used.  A weak spring will stretch out and not rebound.  A strong spring will not stretch enough to measure the distance stretched.

Some springs are made to be compressed.  The coil springs on a car support the weight of the car and compress when a wheel hits a bump.  The spring absorbs some of the force from the bump on the wheel.  The spring then returns to its original height.  This makes the ride more comfortable for the passengers and allows the car to not be so upset by bumps which is especially important in a turn!