What does Hooke’s law state
The force applied to an elastic material is directly proportional (straight line graph) to the extension
What is a limit of proporitonality
Where the x and y data is no longer proportional, so the graph is no longer proportional, in the case of a directly proportional (straight) graph, after the limit of proportionality is reached it becomes curved
What is an elastic limit and what does it apply to
A point where a spring is unable to return to its original shape, because it has been stretched too far. ONLY APPLIES FOR SPRINGS
Name something that is non-hookian
Elastic bands
What type of curve do elastic bands make when measuring force against extension
A hysteresis curve - the trends for loading and unloading are different
What graph does the extension of a spring and the force applied make
Directly proportional so a straight line from the origin
see the Hooke’s Law note to see what a hysteris curve looks like
Oj
What is the area under the loading line in a graph of an elastic band for force against extension
The total energy of the systme
What is the area under the unloading line in a hysteresis curve of an elastic band of force against extension
The useful energy of a system
What is the area between loading and unloading on a hysteresis curve of an elastic band where force is measured against extension
The thermal energy lost
For Hooke’s law, which variable is put on which axis
Force Y
Extension X
How can you do a practical to measure the extension of a spring vs the force applied
- Connect a spring to a clamp, then put a ruler on a lower clamp.
- Measure the length of the spring with no weight attached
- Put weights on the spring
- Measure the length of the spring
- Add more weight
- Repeat until you have around 10 data points
- Repeat the experiment for accuracy
- Calculate the extension for each data point - NEW LENGTH - ORIGINAL LENGTH
What is Newton’s first law
An object in motion will remain in motion unless acted on by another object. An object at rest will remain at rest unless acted on by another object
What is Newton’s second law
F = ma
If a resultant force acts on an object, then it will accelerate
What is Newton’s second law
F = ma
If a resultant force acts on an object, then it will accelerate
What is Newton’s third law
Every action has an equal and opposite reaction
When falling or rising in something like an elevator, do we get lighter or heavier and do we feel heavier or lighter
We feel lighter when falling and heavier when rising but actually our weight does not change
What is terminal velocity
The downwards force is the same as the upwards force, so there is no more acceleration. It is the maximum velocity an object can reach
What does terminal velocity depend on (2)
- Mass
- Surface area
How does a skydiver reach terminal velocity
- Jump out of plane - they start accelerating downwards because their weight is greater than the drag
- The increase in velocity causes the air resistance to increase, so acceleration decreases
- Eventually acceleration reaches zero because they are at a velocity where the force of their weight is the same as the force of the air resistance, so they are at terminal velocity.
What is resultant force
The overall force acting on an object, with forces in the same direction being added and forces in opposite direction being subtracted. If the resultant force is zero, the object doesn’t move but if it isn’t zero, it moves.
E.g. force left = 6N + 5N Force right = 9N
Resultant force = 2N left
What is a velocity time graph
Velocity y axis. X axis is in middle of y axis as velocity can be negative
How do you do an experiment for f=ma
- Weigh the cart
- Set up an apparatus with a cart on a platform, a pulley at the end of the platform and a mass hanging off the platform.
- Pull the trolley back so the mass hangs just below the pulley
- Release the trolley, allowing it to accelerate. Make sure you stop it before it falls off because it is expensive
- Use software like SparkVue to calculate the acceleration
- Repeat steps 2-4 3 times
- Repeat steps 2-5 and continue until you have 10 different force and acceleration measurements
- Plot the data
What is a vector and what is a scalar
Vector - direction and magnitude
Scalar - magnitude only
