Activity type Pendulum system Activity 2.1 and measurement DOWNLOAD e-NOTEBOOK
Making a pendulum to measure time
What to use: Step 2 Consider the most accurate way Each GROUP will require: to measure the time taken for your pendulum to swing. • heavy retort stand • heavy cotton or light string Step 3 • masses (50 g to 1 kg) Tell your teacher when you have a • metre ruler pendulum that swings exactly at the • stopwatch. required rate. Each STUDENT will require: Step 4 When your teacher has checked your • Science by Doing Notebook. pendulum, compare it to those of other groups. What do they have in common? What to do: Put this result on the class board in the table prepared by your teacher. Step 1 Construct a pendulum that takes exactly one second to swing from one side to the other. Discussion: ? 1. When adjusting your pendulum, What does a which variables did you test? simple pendulum 2. Which variable had a significant effect have to do with on the timing of your pendulum? clocks? 3. A simple pendulum can be thought of as a system. What should be included in this system? 4. What energy transformations are happening in the pendulum system? 5. Once the pendulum starts to swing, what keeps it swinging?
Motion and Energy Transfer Student GuideMotion andPart Energy2 Transfer Why do Student all systems Guide run on energy? Part 2 17 Activity 2.1 Pendulum system and measurement Continued
Our metric system of measurement is often referred to as the SI system. This ? Acomes HISTORY from theOF SystémeTHE METRE International, adopted in the French revolution What does a simple during the 1790s. The metre and the pendulum have to do with kilogram both date from this period. the French revolution? This definition for a metre lasted until 1889, when it was replaced by A long-case clock the International Prototype metre, (also called a a standard length marked on a bar grandfather clock) of platinum/iridium alloy kept in the ticks every second. International Bureau of Weights and It has a "seconds pendulum". Measures in Sèvres, near Paris. In 1960, this was again replaced with a unit based on the wavelength of an emission line from Krypton-86. In the 1780s, France was industrialising, but with an In 1983, this was changed again to outmoded system of weights and measures. Different the distance travelled by light, in a regions used different units of length and weight. vacuum, in exactly 1/299,792,458 of a In 1790, the Bishop of Autun (Talleyrand) proposed second. This is today’s standard. a metre be defined as the length of a pendulum of As you can see, standardizing units of period two seconds at the latitude of Paris (45o N). measurement is a very important part This was to be called the seconds pendulum, as it took of science, requiring constant work. one second to swing from one side to the other. The Academy of Science in Paris examined this proposition, Thirty copies of the International Prototype metre were but abandoned it for another standard: one 10 made. This is a picture of one sent to America and millionth of the distance at sea level from the North used as the standard until 1960. Pole to the equator, through Paris. Then began an enormous surveying project to measure this distance. These mapping projects challenged the limits of instrumentation and scientific knowledge of the time.
Motion and Energy Transfer Student Guide Part 2 Why do all systems run on energy? 18 Activity 2.1 Pendulum system and measurement Continued
The pendulum system involves the transformations The 1790s was a dangerous of kinetic and and chaotic time for many gravitational scientists in France and quite potential energy. a few were beheaded at the guillotine. The French revolution began in 1789 with much social unrest. King Louis XVI and his queen, the famous Marie Antoinette, were forced to move from the luxurious Versailles palace back to Paris. In 1792, they were arrested. The king was executed by guillotine the following year and the queen a year later. While much of the French population was impoverished, the royal court lived in The period from 1793 to 1794 unimaginable luxury. Taxes to support this life is known as the Reign of Terror. style were raised from the general population, An estimated 16,000 people, not the nobility. mostly nobles, died at the guillotine in Paris. Many scientists either belonged or were linked to the aristocracy and were at particular risk of execution, but despite the social chaos scientific work continued.
Motion and Energy Transfer Student Guide Part 2 Why do all systems run on energy? 19