Forces and Elasticity Flashcards
What’s the equation that links extension, force and the spring constant?
Force = spring constant * extension or F = k * x
What is elastic distortion? How does it differ from inelastic distortion?
Elastic distortion is when an object is distorted, but returns to its original shape/length when the distorting forces are removed.
This differs from inelastic distortion, where an object doesn’t return to its original shape/length when the distorting forces are removed.
What’s the minimum number of forces needed to stretch, compress or bend a stationary object? Why?
Two. If there’s only one force acting on the object it will move, so at least two forces are needed.
A spring with a spring constant of 25N/m is compressed by 8cm. What is the size of the force used to compress the spring?
2N
F = k * x and 8 cm = 0.08 m, so the force used to compress the spring is 25 * 0.08 = 2N
Ralph stretches a spring to 11 cm using a force of 2N. The natural length of the spring is 6 cm. What is the spring constant of Ralph’s spring?
ANSWER: 40N/m
METHOD: 11cm = 0.11 m and 6 cm = 0.06m, so the extension of the spring in metres is 0.11 - 0.06 = 0.05 m.
k = F / x , so the spring constant is 2 / 0.05 = 40N/m
Ralph calculates the spring constant and predicts that if he increases the force to 5N the extension will be 12.5 cm. However, when he uses 5N the spring extends by 15 cm. Explain why the extension is greater than Ralph predicted.
The relationship between the force applied and the extension of the spring has stopped being linear/become non-linear by 5N, so force is no longer proportional to the extension.
