Question

A spring that can be assumed to be ideal hangs from a stand, as shown. You wish to determine experimentally the spring constant k of the spring. 

a. i. What additional, commonly available equipment would you need? 

ii. What measurements would you make? 

iii. How would k be determined from these measurements? 

Suppose that the spring is now used in a spring scale that is limited to a maximum value of 25N, but you would like to weigh an object of mass M that weighs more than 25N. You must use commonly available equipment and the spring scale to determine the weight of the object without breaking the scale. 

b. i. Draw a clear diagram that shows one way that the equipment you choose could be used with the spring scale to determine the weight of the object, 

ii. Explain how you would make the determination.

Answer 1

a.There are other methods, but answers are restricted to those taught to this point in the year.

i. A device to measure distance and a calibrated mass or force scale or sensor

ii. Hang the mass from the bottom of the spring and measure the spring extension (∆x) or pull on the spring with a known force and measure the resulting extension. 

iii. Use hooke’s law with the known force or weight of the known mass F = k∆x or mg = k∆x and solve for k 

b. Many methods are correct, for example, place the object held by the scale on an inclined plane and find the weight using Wsinθ = k∆x. One could similarly use a pulley system to reduce the effort applied by the spring scale.