Forces: Newtonmeters and Gravity Year 7 WC 1st October 2012

Measuring Forces and Gravity WALT: Describe the difference between mass and weight and be able to use a forcemeter I must be able to use a forcemeter to measure a series of weights I should be able to describe the difference between mass and weight I could correctly predict whether heavier masses will fall faster than lighter ones

What is a force and what do forces do? A force is a push or a pull If an object is not changing speed or direction then the forces acting upon it are balanced For example, what forces do you think are acting on the bottle of water on the bench?

Mass and weight Are they the same? No: Mass = a measure of the amount of matter in an object (KG) Weight = The mass of an object multiplied by the force of gravity, measured in newtons (N).

The force of gravity is 10 newtons per kilogram Therefore a 2kg mass has a weight of 20N (2 X 10 = 20) How much would a 3kg bag of flour weigh in newtons?

What do we use to measure forces? A forcemeter (also called a newtonmeter) You each have a forcemeter and some mass ‘weights’ on your desks You can use the forcemeter to measure the weight of your masses (what is the definition of weight again?). Let’s read p. 373 of the red books together. Try with a few different weights. Do your results confirm what you predicted from calculating the weight in your head (mass X 10)? Write down your observations in a table.

On the moon, the force of gravity is one sixth of the gravity on Earth……….

How does mass affect the time taken for an object to fall? In Galileo’s time, there were 2 groups of people with different theories about how objects of different masses fall: Group A thought that objects of different masses took the same time to fall the same distance. Group B thought that an object with twice the mass would fall twice as fast. …which group do you belong to?

Test your theory….. Take three different masses. Drop your mass from around head height and measure the time it takes each to reach the floor. …write your results into a table What did you find out?

Plenary Complete No. 1 and 2 of exercise 26.3: Gravity on p. 376.