Motion Flashcards
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
What mass unit must you use
Kg
What is the unit of weight
N
What is a force that opposes motion
Friction
What are some forms of friction
Water and air resistance
What equation links work done, force and distance
Work done = force x distance
W=fd
What is the equation for stopping distances
Thinking distance + braking distance = stopping distance
What is thinking distance and what influences it
The distance travelled until a driver hits the brakes. Affected by distractions, alcohol/drugs, tiredness
What is braking distance and what affects it
The distance taken for the brakes to take the speed of the car to zero. Affected by weather, tyres, friction and speed of the car
What is the equation linking final velocity, initial velocity, acceleration and distance
V^2=U^2 + 2as
s = distance
What is the area under a velocity/time graph
The displacement
What is the orbital path of satellites (moons are types of satellite) and comets
Satellites - circular
Comets - eliptical
What is the equation for orbital speed
Orbital speed = (2 x pi x orbital radius)/time
V = (2 pi r)/T
When is the orbit of a comet fastest and when is it slowest
Fastest: at the closest point to the object it orbits
Slowest: at the furthest point from the object it orbits
What is the relationship between the direction of vibration of particles and the direction of the movement of the wave in a longitudinal wave
They are parallel (the same direction) (L for paraLLeL)
What is the relationship between the direction of the vibration of particles and the direction of the movement of the wave in a transverse wave
They are perpendicular
What is the equation for wave speed and what are the units for each
V = f x λ
Speed (m/s) = frequency (Hz or 1/time) x wavelength (m)
What does an oscilloscope do
Measures the frequency of the wave, displaying a graph for x axis time (be careful of units) and y axis voltage (measuring amplitude)
What is the speed of light
3x10^8 m/s
What is the speed of sound
330/340m/s
(Influenced by the air pressure, humidity, temperature etc)
What can happen when a force is applied to an object (3)
The object can:
1. Change speed
2. Change size
3. Change direction
What is the unit N/kg for
Gravitational field strength
What is the unit kg m/s for
Momentum
What equation links speed, time and distance
Speed = distance/time
What is the equation for acceleration
Accélération = change in VELOCITY/time taken
A = (v-u)/t
V = final velocity
U = initial velocity
How do you determine acceleration from a velocity-time graph
The gradient
How do you calculate the displacement (distance) from a velocity-time graph
The area under the graph
Is a force needed to keep an object in motion
No
What letters are used to represent speed, distance and time
Speed - v
Distance - s
Time - t
What is the combined gas law equation
(P1V1)/T1 = (P2V2)/T2
TEMPERATURE MUST BE IN KELVIN
V is for volume
What can you do in the combined gas laws equation if you have constant volume, temperature or pressure
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