Outcomes

Pupils should be able to recall and use the relationship:

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

Get the pupils around the front with the trolley and datalogger set up. Start by pulling the trolley with the force meter attached through the light gate making note of the acceleration. Next tie some string to the trolley and run it over a pulley, add weights to the string and then accelerate the trolley again. Try to keep either the acceleration the same or the force the same (or do both). Could be a good challenge to suitable volunteers. Record the results on the board and go through the idea that if the resultant force changes the acceleration will change and it's not just the pulling force which is important. Get pupils to think about any other forces acting. Pupils will need some notes on N2L, importantly they need to realise it's resultant force which is important (link to previous work on combining forces)

Plenary

Demo Attwood's machine, producing a velocity time graph. Ask the pupils to comment on whats happening in the graph and why.

Homework

Newton's Second Law Questions

Additional Information

Resources Required

Hover pucks

PASCO - light gate with picket tape attachment and picket tape

PASCO - light gate and picket fence for trolley

PASCO - force meter

Trolley

String

Pulley

Some weights

PASCO - Attwoods machine

Textbook References

None

Website References

None

Skills Addressed

Obtaining

Safety/Hazards

Risk Assessment

Notes

None

3-Aut2-I

Contents