Physics 101
Acceleration:
What is acceleration? Acceleration is the time rate of change in velocity. Suppose that an object is moving at a constant velocity and then the velocity changes suddenly, well we would call that change in velocity acceleration. If an object is changing its velocity then it is constant acceleration. To find the average acceleration we use the equation:
A=total velocity/time (vf-vi/time). Acceleration units are expressed in units of velocity/time. Most common units used are m/s/s, m/s^2, or mi/hr/s. Remember! If an object is slowing down, then its acceleration is in the opposite direction of its motion.
The chart below is showing two scenarios of velocity; the first one changing by a constant amount and the second one by a changing amount each second.
Free fall accelerations is when an object is going downwards at 9.8m/s/s
SAMPLE ACCELERATION PROBLEM: A person drops a stone from the window of a building. one second later, she drops another stone. How does the distance between the stones vary with time?
- The position graph for the stones motion is showing that the stone is starting with zero velocity. The graph is curving down because the velocity is increasing while going down. The graph goes towards zero representing the stone falling.
- The velocity graph for the stones motion starts at the axis because on the position time graph it shows that the stone starts with om/s velocity. This is a linear graph showing that the velocity changes throughout the graph by accelerating. The graph is negative representing the stone being thrown.
- Before using the acceleration equation, i had to find the displacement/area so that I had data to put into my equation. The displacement is 3.25. I used the equation y=1/2at^2+voy(t). This equation works because the stones are in free-fall motion.
- 3.25 represents the Y in the equation, meaning this is the total displacement from the top of the roof to the ground. Its negative because you multiply by -9.8m/s^2, which is the acceleration from the gravity of earth.
- T=0.8s which is how long it took for the stones to fall from the roof to the ground.