Acceleration
Objectives:
1. Define acceleration and deceleration.
2. Calculate acceleration and deceleration using the formula given.
Key terms:
acceleration elapsed time free fall
Web Resources:
http://www-physics.ucsd.edu/~phys6/speed.html
http://csep10.phys.utk.edu/astr161/lect/history/velocity.html
Notes:
Acceleration is the change in velocity during a given period of time. Any time there is a change in velocity or the direction of motion acceleration has occurred.
a=Dv/Dt or (v_{2}-v_{1})/(t_{2}-t_{1}) units are d/t^{2 }(m/s^{2})
Must cause and object to speed up, slow down or change direction
At constant velocity acceleration is equal to zero.
Slowing down is called negative acceleration or deceleration.
Practice:
If I fall out of a plane I will begin to accelerate towards the Earth at a rate of 9.8m/s^{2}. If I am 2000 meters above the ground, what will be my velocity after 20 seconds? (Use the formulas: a=v/t or v=at)
The Relationship Between Force and Acceleration:
Remember from working with forces that force is equal to the mass times acceleration. As we increase the force on an object the acceleration increases proportionally. Since the mass does not change as the acceleration increases, we can say that force is equal to acceleration. Therefore, if you double the force you double the acceleration. If you increase the mass at a given force the rate of acceleration slows. Therefore, mass is inversely proportional to acceleration. Rules to follow when equating force to mass are:
Force is directly proportional to acceleration (force ~ acceleration)
As force increases acceleration increases
Acceleration is indirectly proportional to mass (force ~ ^{1}/_{mass})
As mass increases acceleration slows
Total formula: Acceleration = ^{Force}/_{mass} (a = ^{F}/_{m})
Newton's 2nd Law.
Acceleration is produced by a net force on an object and is directly proportional to the magnitude of the force, in the same direction as the force, and is inversely proportional to the mass of the object.