SpeedPages 220-223

https://www.youtube.com/watch?v=gWGLAAYdbbc

TerminologySpeed: The distance an object moves in a certain length of time. Symbol - . It is a ν scalar quantity, it only represents magnitude. It is represented by a number and units, such as m/s, km/h, etc.

Constant speed: When an object travels the same distance for each time interval.

Changing speed: When an object travels a different distance for each time interval.

Average speed: The distance travelled by an object divided by the time it takes to travel that distance.

Instantaneous speed: The speed at a specific instant of time.

CalculationsThe formula used to calculate speed is: vave = d/t

Your change in position is the change in the y axis values, and your change in time is the change in the x axis values. To find the change, you always take your final value and minus your initial value from it. What does this look like?

This is the same formula to calculate the slope of a graph.

You choose 2 random points from a graph (best if they fall on a specific, easy to read plot point) and use them for the calculations.

When calculating average speed, you are calculating the distance travelled/total time elapsed.

Examples

Examples

Examples

Examples

What if you have a word problem?

Write down the information you know, and write down what the question is asking you for. Then, plug the information into the formula. Remember, speed=distance/time. vave = d/t

1. Jane drives at an average speed of 45 mph on a journey of 135 miles. How long does the journey take?

2. Chris cycles at an average speed of 8 mph. If he cycles for 6½ hours, how far does he travel?

3. Nikki has to travel a total of 351 miles. She travels the first 216 miles in 4 hours. What is her average speed for the first part of the journey?

4. Her average speed is the same for the whole of her journey. How long does the whole journey take?

Examples

Tasks For Today

For today, please complete the following.

1. Activity 5-2A in your textbook on page. This will help you practice finding slope from a graph.

2. Uniform Motion Handout. This will help with speed/distance/time word problems.

3. Organizer Handout for definitions/formulas for this unit. This is a good study tool.

We will go over any questions from the uniform motion sheet tomorrow, so please have it done for homework. Remember, your unit test is Dec 18th, so it is important you stay on top of the work assigned to you.