5-FAC-03
Contents
Outcomes
- Pupils should be able to recall and use the relationship:
<math>F=ma</math>
- Pupils should know that that acceleration happens when the forces are unbalanced and that F in the equation represents an unbalanced force.
Specification References
- 1.14 recall and use the relationship between unbalanced force, mass and acceleration:
- <math>F = ma</math>
Starter
- Recap on acceleration and how it is measured using a light gate. Introduce the Newton's Second Law experiment and its set up. This could lead into a discuss where the pupils come up with all the variables and indentifying those which need to be controlled.
- Pupils often have trouble with 0 resultant force = zero acceleration as they all are very used to friction. Try these two things:
1) Draw a person throwing a ball into the air, ask the pupils to make a quick table with one colum for direction of movement and one for resultant force. Then draw the balls flight and identify one place on the way up, one at the top and one on the way down. Have pupils draw arrows to show the direction of travel and of the force. All will get the direction correct, most will get the force incorrect. The only force they should be thinking about is weight acting downwards.
2) As a second more physical demonstration use the hover pucks with some picket tape. Just give the hover puck a little push and see the result. After the initial push to accelerate, you should get a nice straight line distnce time graph and a constant velocity with zero acceleration.
Main Body of Lesson
Newton's Second Law Experiment
- In groups of 2 or 3 pupils will carry out two experiments using a light gate, laptop, trolley, ramp, 100g masses, pulley and picket fence. * They will investigate how changing the mass of the trolley and the force acting on the trolley will affect its acceleration. It is possible to save time by having half the class change mass and other half changing force.
- Before beginning there is an opportunity to discuss all the other factors affecting the acceleration of the trolley. Dynamic friction can be eliminated by lifting the ramp until the trolley travels down the ramp with a constant speed after it is given a little nudge. This can be done by adding books under one side of the ramp. Pupils can use the light gate to ensure that the trolley is indeed not accelerating down the ramp.
- Once friction compensation is complete the rest of the set up can be completed. There is no need for the trolley to travel too far after passing through the light gate, so trolleys should be released and then caught directly after a reading.This will allow three readings to be taken rapidly.
- Pupils should record the results in two separate tables. Ensure that they are also recording the control varibles.
Plenary
Graphing
- The end of this lesson should be spent plotting the two graphs and observing their shapes. Pupils can plot a third graph of acceleration against 1/mass. This will confirm the inverse relationship. Show the pupils how to quote values from the graph to show that as force double acceleration doubles plus as mass doubles acceleration halves.
Homework
- Newton's Second Law Questions
Additional Information
Resources Required
Textbook References
- None
Website References
- None
Skills Addressed
Safety/Hazards
Risk Assessment
Notes
- None
