1. P2.3 Forces in Action

2. 28-Nov-18
Springs
Starter – How many forces must be applied to stretch, bend or compress an object?

3. Practical investigation
How can we do a practical to investigate how much a spring extends depending on the force applied to it?

5. Force (N)
Starting length (m)
Extended length (m)
Extension (m)
Average Extension (m)

6. Graph

7. Spring constant
We should be able to calculate the spring constant from the gradient of the straight part of the graph. Gradient = Change in y / Change in x = Change in extension / Change in Force= Spring Constant (N/m)

8. SPRING CONSTANT
Force = spring constant x extension (N) (N/m) (m) F = kx

9. Elastic Limit?
Does the line remain a straight line?

10. Energy stored in the spring
Force (N)
Average Extension (m)
Energy Stored (J)
GPE lost (J)

11. The Conservation of Energy
Energy cannot be created or destroyed. It is converted into different forms. For a roller coaster, energy is transformed between gravitational potential and kinetic energy. The principle of conservation of energy tells us that gravitational potential energy (GPE) at the top of a roller coaster = kinetic energy (KE) at the bottom + energy transferred as heat and sound.

12. Gravitational Potential Energy
The gravitational potential energy (GPE) of an object is the energy stored due to:
its position in the Earth’s gravitational field (height)
its mass.
You can calculate GPE using this formula:
GPE = mass x gravitational field strength x vertical height
(J) (kg) (N/kg) (m)

13. Energy stored in the spring
Force (N)
Average Extension (m)
Energy Stored (J)
GPE lost (J)

14. Kinetic Energy KE= 0.5 x mass x velocity2 (kg) (m/s)
Kinetic energy depends on the mass and velocity of an object.
KE= 0.5 x mass x velocity2
(kg) (m/s)

15. Rollercoaster

16. Height dropped from (m)
Energy at start (J)
Height reached 1 (m)
Height reached 2 (m)
Height reached 3 (m)
Average height reached (m)
Energy at highest point (J)