title: p2 revision 11a5 objectives how do we measure the extension of an object when stretched? –...
TRANSCRIPT
TITLE: P2 Revision 11A5
Objectives• How do we measure the extension of an object
when stretched? – grade C• What is the spring constant of a spring? – grade C• What is Hooke’s law? – grade C
KEY WORDS:
StretchSquash
ExtensionEnergySpring
constant force
NewtonsMetre
ExtensionProportional
Limit of proportionalit
y
Outcomes:• Use the revision PowerPoint to complete the set
activities in preparation for your mock examination
• Complete the terminal velocity card sort with Mrs Potts
What is meant by Resultant Force?(Use to help with slide 3 and 4)
The differences between the forces acting on an object to create an overall single force.
Resultant Force = zero when an object is stationary or at a constant speed if moving
Resultant Force = not zero when an object is accelerating or decelerating
What is the resultant force for each car?
A =
B =
DESCRIBE the motion of each car and EXPLAIN why?
A =
B =
Why have speed limits?
The faster a vehicle is driving, the longer it will take to stop – the overall distance this takes is the stopping distance.
stopping distance = t_______ distance + b_____ distance
What affects thinking distance?The thinking distance is the distance a vehicle travels in the time it takes for a driver to react to a situation and apply the brakes.
What factors will affect thinking distance? – 3 images
Is a tired driver as dangerous as a drunk driver?
• http://www.bbc.co.uk/learningzone/clips/risks-of-driving-when-tired/8323.html
What affects braking distance?The braking distance is the distance a vehicle takes to stop once the driver has applied the brakes.
What factors will affect braking distance? – 3 images
Factors affecting stopping distances
What does the graph show?
What is the difference in speed of the cars?
Velocity time graphs – label the points
• A• B• C
Acceleration
Deceleration
Constant speed
A
B
C
Investigation
• What is meant by extension?
Limit of proportionality?
• What is meant by this term?
• Label with a star the limit of proportionality on the rubber band and polythene strip
Hooke’s Law
• The extension of an elastic object is directly proportional to the force applied, provided that the limit of proportionality is not exceeded:
Formula:• F = k x e– F is the force in newtons, N– k is the spring constant in newtons per
metre, N/m– e is the extension in metres, m
The spring constant
• The spring constant is the force per unit extension needed to extend the spring, assuming you do not exceed the limit of proportionality.
• The stiffer a spring is, the g_____ its spring constant.
Complete the example (grade C)
• A spring has a spring constant of 25 N/m. How much force is needed to extend the spring by 0.1m?
• F = k x e• F =
Using bbc bitesize (grade C)
• Resaerch the equations and UNITs for each one and an example calculation:
• Momentum equation• Work done equation• Weight equation
• Print out the handout as a revision tool