Year 10 Physics - Forces, Motion, & Energy: Lesson 2 Notes

Area of Study 1: Forces, Motion, & Energy - Lesson 2

  • Objective: Analyze straight-line motion under constant acceleration, identifying parameters as vectors or scalars graphically, numerically, and algebraically.

  • Goal: Explore how changing distance and time affects speed/velocity.

  • Success Criteria:

    • Differentiate between scalar and vector quantities.

    • Calculate speed and velocity.

    • Consider ways to improve accuracy and precision in data collection.

Key Vocabulary

  • Distance

  • Displacement

  • Speed

  • Velocity

  • Scalar Quantity

  • Vector Quantity

  • Acceleration

Scalar and Vector Quantities

  • Scalars: Quantities with only magnitude (size).

  • Vectors: Quantities with both magnitude and direction.

Distance vs. Displacement

  • Distance (d): A scalar quantity that measures the total distance traveled.

    • SI Unit: meters (m)

  • Displacement (x): A vector quantity measuring the shortest distance between two points.

    • SI Unit: meters (m)

Speed vs. Velocity

  • Speed (s): A scalar quantity indicating "how fast an object is moving."

    • It represents the rate at which an object covers distance.

  • Velocity (v): A vector quantity referring to "the rate at which an object changes its position."

Speed and Velocity Equations

  • 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)

    • \Delta = change = final - initial

Speed Equation

  • s = \frac{d}{t}

    • s = speed (m/s)

    • d = distance (m)

    • t = time (s)

Helpful Hints: Unit Conversion

  • Converting between km/h and m/s:

    • km/h ÷ 3.6 = m/s

    • m/s x 3.6 = km/h

Checkpoint Examples

  • Example 1: A dog chases a ball 40m west in 5 seconds.

    • Calculate the speed of the dog.

    • Calculate the velocity of the dog.

    • V: List the variables

    • E: Which equation/s connects these variables?

    • G: Go! Substitute and solve

  • Example 2: A cat runs around the neighborhood for 10 minutes at an average speed of 1.5 m/s. How far does the cat cover in this time?

    • V: List the variables

    • E: Which equation/s connects these variables?

    • G: Go! Substitute and solve

Your Turn Questions

  • Question 1: A car travels 540 km north in 6 hours.

    • What speed did it travel at (in km/h)?

    • What is the car’s average velocity in m/s?

  • Question 2: A whale swims at a constant speed of 8 m/s for 17 seconds. What distance did it travel?

  • Question 3: How long does it take to travel a distance of 672 km at a speed of 96 km/h?

  • Instructions:
    * V: List the variables
    * E: Which equation/s connects these variables?
    * G: Go! Substitute and solve
    * In your book write out the question and the answer, as well as working out (working out = the equation and full substitution as well as the answer)

How Fast Can You Run? Experiment

  • What data will you need to determine your speed?

  • How can you increase the precision and accuracy of your data?

    • Accuracy: How close a measurement is to the true value.

    • Precision: How close multiple measurements are to each other. Precise measurements have values close to the mean.

      • Repeating an experiment improves precision through statistical averaging, but doesn't affect accuracy, as systematic errors don't average out.

Experiment Procedure

  • Perform at least three trials to measure running speed.

  • Optional: Measure skipping, moonwalking, or rolling speed.

  • Record data in a table:

    Distance (m)

    Trial 1 (s)

    Trial 2 (s)

    Trial 3 (s)

    Average time (s)

    Speed (m/s)

    Running

    Moonwalking

    Rolling