PS2.1 - Acceleration Defined

Bucket o' Cars

To explore ideas about motion – description of an object's movement not why they move. Before we can discuss causation, we will describe the manner in which objects move.

Mark off a section of on your table with a Start line and Finish Line 50 cm apart.
Individually, set each car into motion before the START line
Observe the motion of each of the cars between the START and FINISH lines.
Write a description of the motion of each type of car. Describe the motion of the car - not the car or what makes it do what it does.
1. Pull back car
2. Hot wheels car
3. Battery car
Using a minimum of 5 motion maps, illustrate the motion of each car.
Sketch a graph of the motion of each car, on the same graph. Consider the point at which you release the car as time 0 sec and position 0 m for each car.
Rank type of motion you think is easiest (or simplest) to hardest (most complex) to study, and why?
List and define key words that you have used when you described the motion of the cars that you think are important.
1. Research the definitions of the terms you listed. How do the definitions used by physicists differ from your personal definitions.

What does it mean to accelerate?

Uniform Acceleration in one Direction

Constant Velocity (No Acceleration) =

Motion in One Direction + ZERO acceleration

If the Tom, the cat, and Jerry, the mouse, travel the same distance each second in one direction, they are traveling at a constant velocity. They are not accelerating. The Net Force acting on the object is 0-N.

Positive Acceleration =

Forward Motion in One Direction + Increase in Speed

The motion of the car is in a straight line. The acceleration is in the same direction as the motion of the car, so it can be said the car has a positive acceleration.

Negative Acceleration ('Decelerating') =

Forward Motion in One Direction + Negative Change in Speed

The plane is moving in one direction, however the acceleration is in the opposite direction, causing the plane to slowdown. We can say that the plane has 'decelerated' or has a negative acceleration (better).

Negative Acceleration =

Backward in One Direction + Negative Change in Speed

The direction of the acceleration is relative to the zero point (starting point) and agreed positive direction. In the example above, it is a similar motion to the positive acceleration above, however, the driver is facing in a positive direction and the car is moving in a negative direction.

Constant Speed + Changing Direction = Acceleration (centripetal)

In this incredible music video by the new Queen of Pop, Dua Lipa (her stunt double and partner) are accelerating towards the inside of the circle. The Spin at ~2:20 into the video.

Bouncing Cart Discussion

Bouncing Cart Description

From the graphs above, answer the following:
1. Before time A, describe the motion of the cart.
2. Indicate on both graphs, the following:
  1. Where the cart is stopped.
  2. Where the cart is traveling at the greatest velocity.
3. Using a sketch of the cart on a ramp, indicate where the cart is at each of the times shown.
Using a series of sketches, show what is happening between time B and D.
At time F, compare the maximum velocity of the cart just prior to the dashed line and just after the dashed line. What would cause the differences between the two velocities.
Answer each of the following:
1. In a position-time graph, a straight horizontal line represents a particle that is: a) Accelerating positively b) Moving with constant velocity c) At rest d) Decelerating
2. On a velocity-time graph, a horizontal line at the zero velocity level indicates that the object: a) Is accelerating uniformly b) Is moving with constant positive velocity c) Is momentarily at rest d) Is decelerating uniformly
3. Which of the following describe the relationship between the slope of a position-time graph and the velocity of an object:
  1. The steeper the slope of a position-time graph the slower the velocity.
  2. The steeper the slope of a position-time graph the faster the velocity.
  3. A positive slope on a position-time graph represents a positive velocity.
  4. A positive slope on a position-time graph represents a negative velocity.
Using both the position-time and velocity-time graphs, answer the following:
1. How does the bounce height of the cart change with each successive bounce?
2. How does the velocity of the cart change with each successive bounce?
3. What are some aspects (shape, slope, max point, min point) that remain constant between the bounces?
4. Does it exhibit a consistent pattern?
5. Based on the data given could you predict the height of the fourth bounce?
Suppose a steeper ramp were to be used. If the cart is released at the same position on the ramp and the same spring is used, SKETCH the new position-time and velocity-time graphs.

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