Forces, Motion, & Energy Flashcards

Forces, Motion, & Energy

Area of Study 1: Forces, Motion, &Energy - Lesson 3

• Identify parameters of motion as vectors or scalars.

• Analyze, graphically, non-uniform motion in a straight line.

Goal

• Analyze kinematics graphs (displacement-time, velocity-time, and acceleration-time).

Success Criteria:

• Define acceleration as a change in speed and/or direction (change in velocity).

• Calculate acceleration mathematically.

• Interpret information presented as kinematics graphs.

• Question: How do speed cameras work?

Acceleration

• The rate at which velocity changes with time, considering both speed and direction.

• Acceleration can occur if an object speeds up, slows down, or changes direction.

Speed & Velocity

• Speed: $s = \frac{d}{t}$

  • $s$ = speed (m/s)

  • $d$ = distance (m)

  • $t$ = time (s)

• Velocity: $v = \frac{\Delta x}{t}$

  • $v$ = velocity (m/s)

  • $\Delta x$ = displacement (m)

  • $t$ = time (s)

Acceleration (Continued)

• Acceleration due to gravity ($g$) is the acceleration of an object due to gravitational force.

• On the surface of Earth, $g = 9.81 \text{ m/s}^2$.

• The value of $g$ is different on different planets due to varying masses.

Acceleration Formula

• $a = \frac{\Delta v}{t}$

  • $a$ = acceleration (m/s²)

  • $\Delta v$ = change in velocity (m/s)

  • $t$ = time (s)

• $a = \frac{v<em>f - v</em>i}{t}$

  • $a$ = acceleration (m/s²)

  • $v_f$ = final velocity (m/s)

  • $v_i$ = initial velocity (m/s)

  • $t$ = time (s)

Displacement-Time Graphs

• For motion in 1-dimension.

Checkpoint: Acting out displacement-time graphs

• Place markers 1m apart from negative 4 to positive 4.

• Start the stopwatch and try to match your motion to the graph. The person timing you should give you feedback on how you went.

• Swap roles and repeat the activity until everyone in your group has had a turn.

• Finished early? Create your own to act out.

Velocity-Time Graphs

• For motion in 1-dimension.

• Includes positive acceleration, negative acceleration and zero acceleration

Converting between Kinematics Graphs

• It is possible to convert between displacement-time, velocity-time, and acceleration-time graphs for motion in one-dimension (left/right, up/down, north/south, etc.).

Checkpoint

• Use the velocity-time graph to draw a displacement (s) - time graph and an acceleration - time graph.

• Draw an approximate velocity-time graph and then use that to draw an approximate acceleration-time graph for the four displacement-time graphs.

Instantaneous vs. Average Speed

Instantaneous Speed

• The speed of an object at a particular moment in time.

• If direction is included, it becomes instantaneous velocity.

Average Speed

• The average speed formula is given by the total distance traveled divided by the time taken to cover that distance.

• Assume you’re being asked for average speed in VCE physics.

Okay, here's a simplified explanation of kinematics graphs:

• Displacement-Time Graphs: These graphs show how an object's position changes over time. A straight, sloped line means the object is moving at a constant velocity. A curved line indicates acceleration (changing velocity). The steeper the slope, the faster the object is moving.

• Velocity-Time Graphs: These graphs illustrate how an object's velocity changes over time. A straight, sloped line indicates constant acceleration. A horizontal line means the object is moving at a constant velocity. The area under the curve represents the displacement of the object.

• Acceleration-Time Graphs: These graphs show how an object's acceleration changes over time. A horizontal line indicates constant acceleration. The area under the curve represents the change in velocity of the object.