5. Hooke’s Law Flashcards
What is the aim of the springs and rubber bands practical?
Investigate relationship between force and extension
Describe the method for the Hooke’s law practical
- Set up apparatus
- Record initial length of spring (should subtract this from all further measurements to find extension)
- Add 100g mass to spring
- Record mass and new length of spring
- Add another 100g mass to spring
- Record new mass and new length of spring
- Repeat
- Remove all masses and repeat 3 times and take mean average of extension
- Calculate the force by multiplying the mass x gravity
- Plot graph force x extension
What are the possible errors of the experiment?
- make sure measurements with ruler are taken at eye level to avoid parallax error
What are the safety precautions?
- goggles in case spring snaps
- stand up so no feet are under masses
- g clamp to secure clamp stand to desk so that it does not fall over
What is Hooke’s law?
The extension of a spring is directly proportional to the applied load force
What does directly proportional mean?
- Force extension graph will be a straight line through the origin
- If the force doubles the extension doubles
- Force divided by extension is constant
How do you calculate the spring constant?
F= kx (where F = force, k = spring constant, x = extension)
Constant= F/x (stiffness of spring)
Thus if you double the force, you double the extension (because k is always constant)
What is elastic behaviour of a material?
When the stretching force is removed the object will return to its original shape
What is plastic behaviour of a material?
When the stretching force is removed the object will not return to its original shape, it will be permanently deformed
What is the gradient equal to?
The spring constant
What happens when the spring goes above the elastic limit?
- wont return to its original shape
- unloading extensions will be larger than the loading extensions
What is the unit for spring constant?
N/m not Nm! Which is unit for moment
