Motion

Questions From Yesterday Which design covered the most distance? Why do you think this is the case? Which design covered the least distance? Why do you think this is the case? How accurate do you think your measurements were?

Measurements and Calculations

Plan of Attack Accuracy Rounding Converting Solving Equations

Accuracy and Precision Accuracy is defined as how close a measured value is to the actual value (or target value). Precision is defined as how close the measured values are to each other.

Accuracy: Rounding When we work with quantitative data (measured values) we need to know how to measure, record, and do calculations. Seems pretty straightforward, measure, record and write the answer right…RIGHT? There are certain “rules” that we use every day with rounding. Clock says 12:17, we round to 12:20 because it looks closer and we want lunch sooner. The rule for rounding numbers is as following: If the digit after the digit to keep is 5 or greater, round up. If the digit is less than 5, round down.

If we want to keep 1 decimal, round the following: 7.13 cm 2.38 cm If the digit after the digit to keep is 5 or greater, round up. If the digit is less than 5, round down. Accuracy: Rounding Example If we want to keep 1 decimal, round the following: 7.13 cm 2.38 cm 5.50 cm 5.55 cm 7.49 cm 8.01 cm

Rounding This “rule” is universal and everyone throughout the world use it. It is not useless. When doing calculations we ONLY round at the end when there is an answer. NOT during a multistep calculation.

Example with rounding Find the volume of a cube. Round to 2 decimal places. 𝑉𝑜𝑙𝑢𝑚𝑒=𝑙𝑒𝑛𝑔𝑡ℎ 𝑥 𝑤𝑖𝑑𝑡ℎ 𝑥 ℎ𝑒𝑖𝑔ℎ𝑡 Length = 2.22 cm Width = 3.45 cm Height = 5.05 cm Answer: 38.67795 cm3 Real Answer: 38.68 cm3

Converting Sometimes you will need to convert one measurement into another one. Think of going from meters to kilometers and vise versa. You will need to some of the more common conversion factors. Time: seconds to minutes, to hours, etc… Distance: mm to cm, to m, to km, etc… Pay close attention to units!

Converting Examples 10.0 cm to km 4 hour to seconds 6.4 km to m

Solving Equations It is easier to rearrange equations before you start to solve for quantities as it can save quite a bit of trouble. This is an essential skill that does NOT automatically click for some. Once you understand how it works, THEN it will click. Practice. This is the groundwork for the unit. Start with something simple like the speed formula. Rearrange for distance. Rearrange for time.

Solving Equations Rearrange for time. Rearrange for distance.

Practice In the textbook, go to page 141 and do the first 3 Questions.