Lesson 5: Elastic Potential Store

Question 1

What is elastic potential energy?

Answer 1

Elastic potential energy is energy stored in strecthed/ compressed objects.

Question 2

What 2 factors affect the elastic poential energy stored in a spring?

Answer 2

• Spring constant
• Extension

Question 3

What is the extension?

Answer 3

Extension is the change in length when a string is stretched.

Question 4

What is the spring constant?

Answer 4

The spring constant is how much force is required to extend a spring. ie. the stiffness.

Question 5

Does the elastic potential store depend on:
a.) the total length of spring
b.) the extension of the spring

Answer 5

b.) the extension of the spring.
For example:
A spring that is 10cm been extended to 15cm will have less energy than a spring that is 10cm long compressed into 3cm .

Question 6

What are the units for spring constant?

Answer 6

N/m

Question 7

What are the units for extension?

Answer 7

m

Question 8

What is the equation for elsatic potential energy?

Answer 8

½xspring constant x extension²

Question 9

When doing the spring practical, how can you tell which spring has a higher spring constant from the graph?

Answer 9

If they both require the same force, the one that extended the less will have a higher spring constant. (more force is required to stretch it)

Question 10

How is spring constant represented on a graph?

Answer 10

Gradient: force/ extension

Question 11

What is the equation linking force, spring constant and extension?

Answer 11

F=ke
Force = spring constant x extension

Question 12

What does Hooke’s Law say?

Answer 12

Hooke’s Law states that the extension of a spring is proportional to the force applied.

Question 13

How do you work out the elastic energy at different extensions?

Answer 13

You find the area under the graph.
1/2 x extension x force = Nm
Nm = J

Question 14

What is the limit of propertionality?

Answer 14

This is where the force is too high, that a spring will not return to its normal shape.
The Force is no longer proportional to extension

Question 15

What is meant by elastic behaviour?

Answer 15

This is where a spring will return to a normal shape once the force has been released.

Question 16

A spring of spring constant 50N/m is stretched so the extension of the spring increases from 0.3m to 0.6m. How much extra energy is stored in it?

Answer 16

• You must calculate the energy stored in each extension.
• Then, you work out the extra energy stored in the greater extension, by taking away the values.

Because measurement of unstretched spring isn’t given

Question 17

How do you work out the spring constant if a graph has force on x axis and extension on y axis?

Answer 17

• Simply do x/y
  Force/ estension = spring constant.