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Dynamics I - Coggle Diagram
Dynamics I
Newton's 2nd law
Acceleration of an object is directly proportional to the resultant force acting on the object, but inversely proportional to the mass of the object
The larger the resultant force acitng on an object, the more the object accelerates
An object with a larger mass will accelerate less than one with a small mass for a fixed resultant force
When the resultant force is 0, the acceleration is 0
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Inertial mass is a measure of how difficult it is to change the veloity of a moving object, it's the ratio of force over accelration
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Newton's 1st law
An object in equilibrium will either remain at rest or continue at constant veolicty unless acted on by a resultant force
If the resultant force on a moving object is zero, it'll carry on moving at the same velocity (at the same speed and direction)
If the resultant force is zero, the object is in equilibrium and will either remain stationary or at a constant velocity
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If a resultant force acts on the object, it will accelerate, meaning its velocity will change, so either direction of speed will change, or both
Newton's 3rd law
When body A exerts a force on body B, then body B exerts on body A a force that is equal, opposite in direaction and off the same type
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Example
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Equal and opposite, and acting on different objects
Investigating motion
Method
1) Set up your apparatus by plugging in light gate A and B into the data logger, and placing each light gate at the start and end of the ramp, connect a pulley to the table and pass a string through which has a hook attatched, this is where you will add mass. Keep the ramp at a slope to reduce the effect of friction
2) Set up a trolley so that it has an interrupt card attatched to the top of the trolley, measure the length of the card and input this into the data logger, the light gates will measure the velocity of the card and then calculate the acceleration of the trolley
3) The weight of the hook will provide an accelerating force, start with 50 grams (0.5 N) and let the trolley roll down making sure someone is at the end to stop it, record the acceleration and repeat 2 more times, taken an avergae acceleration
4) Remove a weight from the hook and place it on top of the trolley, this will keep a constant mass in the system
5) Repeat steps 3 and 4 until you have done all masses, even with just the hook and no masses, this is 10 grams (0.1N)
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Explaining the result
Newton's 2nd law states that force and acceleration as directly proportional, F = ma
By transferring masses from the hook to the trolley, you are increasing the force without changing the mass of the whole system
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Terminal Velocity
Freefall
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Weight always acts downwards, the resistance of the fluid causes and upward force
As the falling object accelerates, the resistance forces icnrease
When the resultant force is zero, the object falls at a constant velocity, called terminal velocity
Example
The force of gravity pulls the skydiver downwards, air resistance is small, resultant force is larger, causes acceleration
As velocity increases, air resistance increases. As weight remains constant, the resultant force gets smaller and acceleration decreases
When air resistance is equal and opposite to the weight of the skydiver, the resultant force (and acceleration) are zero, the skydievr has reached terminal velocity
The skydiver opens the parachute, air resistance increases due to the larger surface area, resultant force is upwards (acceleration downwards in negative), the skydiver's velocity reduces and air resistance decreases until is equals wieght
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