# SP15 - Forces and Matter ✓ Flashcards

SP15a - What are the three things a force can do to an object?

- Change shape(/size)
- Change direction
- Accelerate (Decelerate)

SP15a - What is the name for a force changing the shape of an object and what is required for it to occur?

It is called deformation and requires two forces rather than just one.

SP15a - What does it mean if an object elastically deforms?

The forces change the object’s shape but it returns back to its original shape when forces are removed. (e.g spring, diving board, and archer’s bow.)

SP15a - What does it mean if an object inelastically deforms?

The forces change the object’s shape and it doesn’t return back to its original shape when forces are removed. (e.g Clay, Blu-tac, and spoons.)

SP15a - How may some objects behave elastically and inelastically?

Some objects (like springs for example) will behave elastically. However, when the forces exceed a certain amount, they will become permanently deformed, behaving inelastically and keeping its new shape.

[Life Lesson #44: Don’t overextend yourself]

SP15a - What is the extension of a spring?

The change in length of a spring when a force is applied

New length - old length = extension

SP15a - How would you describe the relationship between force and length of a spring

It is a linear relationship (straight line) as long as the spring behaves elastically.

Once it is permanently deformed, the relationship is non-linear (curved).

SP15a - What is the relationship between extension and force of a spring and rubber band?

- Spring: They are directly proportional as it would be a straight line through the origin.
- Elastic band: It behaves completely inelastically with a non-linear relationship

SP15b - What is a spring constant?

The force (N) required to produce and extension of 1 metre

SP15b - What is the equation linking force and spring constant?

F = k × x

Force (N) = Spring constant (N/m) × Extension (m)

SP15b - What is the relationship between force and extension?

F ∝ x (Directly proportional)

SP15b - What does the gradient of a Force/extension graph show you?

Sign gradient is Δy÷Δx it would be force/extension which will give you the spring constant of a spring

SP15b - How may you be able to tell that a spring has a higher spring constant by holding it?

Stiffer springs have a higher spring constant (As they require more force to extend)

SP15b - How do you calculate the work done when stretching a spring?

E = 1/2 × k × x²

Energy transferred by stretching (J) = 1/2 × Spring constant × Extension²

SP15b CP - Describe how to find the spring constants of different springs.

- Set up your equipment as shown
- Measure the length of the spring without any weights at eye-level
- Add 1 newton (100g) weights one at a time, measuring the new length at eye level each time
- Take away the original length from all your values to get the extension
- Repeat a few times and take the average of your results for reliability
- Plot a graph of force/extension and calculate the gradient of the line. This will be the spring constant
- If you want to find the work done for a particular extension, square that extension, divide by 2 and then multiply by the spring constant