Acceleration

Book pages 48 -59

1. The quantity that describes the rate of change of velocity in a given time interval is called acceleration.

2. A car going coasting from the top of a hill to the bottom of a hill; increasing speed by the time it reaches the bottom. Also, a roller coaster starting at 0 mph and picking up a 60 mph speed within a few seconds.

3. A change in velocity can be the same amount, but the times can be much different. For example, a car could go from 40 mi/h to 0 mi/h in about 5 or so seconds but if it needed to slam on the breaks quickly to avoid hitting something it could go from 40 mi/h to 0 mi/h much faster; maybe 2 seconds.

4. To find the rate at which velocity changes per time interval, you take the final position minus the initial position divided by the final time minus the initial time.

5. Units are meters per second squared.

6. If the stopping time of a shuttle bus was very short, a person on the bus would be thrusted forward. They could fall if they were standing up.

7. When the velocity in the poitive direction is increasing, the acceleration is positive. When the velocity is constant, the acceleration is 0. When the velocity in the positive direction is decreasing, the acceleration is negative.

8. Similar to the answer in number 7, the slope shows how the acceleration is going. if the slope is positive, then the object is accelerating. If the line is going down, then the acceleration is decreasing.

9. If an object has constant acceleration then its average acceleration is 0.

10. Displacement is the relationship between velocity and time. It depends on acceleration, initial velocity, and time. The equation to find displacement is time times velocity (d=tv). In the speed lab the displacement showed which direction the car was moving. If the displacement was negative that meant the car was moving towards you and if it was positive that meant the car was moving away from you.

11. For an object traveling with constant acceleration, the average velocity is equal to the average of the initial velocity and the final velocity. In the rolling ball lab, the velocity increases as the ball rolls farther down the ramp.

1. How is the velocity changing every second? The velocity is decreasing as the object goes up and then increases as it goes down. The velocity is - 9.8 m/s. 2. If you were falling for 1 second how fast are you traveling in (miles/hour)? Roughly 9.8 m/s multiplied by two would give you about 20 miles/hr. 3. Does mass effect the rate at which veloctiy changes for freefalling objects? No it does not. The mass does not effect the speed at which an object falls.
 * Freefall Acceleration:**


 * __ Up and Down Motion  __**

1. What is the rate at which velocity changes through the entire motion? You have an initial velocity that is greater then 0 so that the object can can move up. Then as the object begins to move up the velocty at which it is traveling slows down. Once the object reaches its max height it falls back down due to the laws of gravity. The object travels 9.8 m/s every second. 2. Where is the rate of velocity change marked on the graph? You find it on the velocity vs. time graph, and thats the slope. The slope is the red line and it never changes. It is always -9.8. 3. What is the starting speed? The starting speed is not zero, It is around 9.8 m/s or roughly 25 miles/hr. 4. What is the speed at max height? The speed at the objects max height is 0 m/s. 5. What is the speed right before it hits the ground? It is the same speed that it was when it started (9.8 m/s)