5-FAC-01

Outcomes

• Pupils should be able to recall and use the relationship:

<math>avg speed = distance moved/time taken</math>

• They should appreciate the difference between average speed and instantaneous speed.
• Pupils should know how to measure avg speed practically including an understanding of how a data logger measures velocity.
• Pupils should be able to recall and use the relationship:

<math>a = (v - u)/ t</math>

• Pupils should have an appreciation for how a light gate measures acceleration using a double interrupter or a picket fence.
• Pupils should be able to recall and use the relationship:

<math>F = ma</math>

• Pupils should understand the proportionality relationship between force and acceleration and link this to straight line graph obtained practically.
• Pupils should understand the inverse proportionality between mass and acceleration and link this to the curve obtained practically.
• Pupils should understand that acceleration comes from an unbalanced force.
• Pupils should appreciate that speed, mass, road condition and reaction time are the factors that affect vehicle stopping distance.

Specification References

• 1.3 recall and use the relationship between average speed, distance moved and time:

<math>avg speed = distance moved/time taken</math>

• 1.4 recall and use the relationship between acceleration, velocity and time:

<math>a = (v - u)/ t</math>

• 1.14 recall and use the relationship between unbalanced force, mass and acceleration:

<math>F = ma</math>

• 1.17 describe the factors affecting vehicle stopping distance including speed, mass, road condition and reaction time.

Starter

• Brain storm: What is speed? What is velocity? What is the difference between them? Revise vector and scalars.
• Discuss how the speed of car can be measured. What equipment would one need?
• Handout a copy of data including the distance and time for two car journeys over the same
• How is average speed measured? What is the difference between average speed and instantaneous speed?
• light gate? single card? double interrupter?
• introduce them to picket fence.

Main Body of Lesson

• 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 before 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.
• Graphing

Homework

• Pupils are to write a conclusion for each experiment. They must include a discussion of the graphs where they look at the classic shape. (Proportional and inversely proportional) They must also quote values from their graphs to show trends. They must also try and say why it has happened.
• There is also a question sheet on using the equations.
• Question sheet on stopping distance - use of speed = distance/time

Additional Information

Textbook References

• None

Website References

• None

Skills Addressed

• Obtaining

Safety/Hazards

• A tank with water in it will be heavy and so is only to be moved by the technician; please refer to the Manual handling section of the Laboratory Lessons Health and Safety Risk Assessment
• When using springs, goggles must be worn
• The main risk is from the vacuum pump and apparatus. The specific risk assessment must be read before using the apparatus.
• General Laboratory Health and Safety Risk Assessment

Notes

• None

Forces & Matter Outline

Forces & Matter