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Weight Weight The earth exerts a force on everything This force is called gravity What does gravity do? Hold your pen up and then let go Why does this happen Weight The force the earth exerts on me is called my weigh The weight of a body is the force pulling it towards the center of the earth Like all forces, weight is measured in newtons Weight So what is your weight, how do you measure your weight We are all made of matter, some people have a grater matter than others The more matter an object has the greater will be the force acting on it A block of lead would have a greater mass than a block of wood of equal size Force of gravity acting on the block of lead would be greater than the force of gravity acting on the block of wood. The block of lead has a greater weight So the weight of a object is determined by two things the mass of it, and the fore of gravity acting on it Weight Does your weight change when your in the moon or space Your weight changed because the pull of gravity on it changes What is weight again = The force the earth exerts on an object Will a litre of milk weigh the same on the earth, moon and space Weight The litre of milk will be 6 times lighter on the moon compared to earth The moon is one-sixth the size of the earth The force of gravity acting on an object is one-sixth, of the force acting on earth The moon has a force of 1.67 on 1kg The litre of milk will be weightless in space Your weight is zero in space, that’s why you can float because there is no force of gravity acting on you Things also wheigh less on the top of a mountain Instead of a force of 10 N it would be 9 N Class Activity Do calculation 1, 2, 3, 6, 6 minutes Calculations 4, 5 homework Calculations 1 A litre of milk (1kg) on the earth weighs 1kg x 10N = 10 N/kg A litre of milk on the moon weighs 1 kg x 1.67N = 1.67 N/Kg A litre of milk in space weights 1 kg x 0 = 0 N/kg A litre of milk on the top of a mountain weighs 1 kg x 9N = 9 N/Kg Calculation 2 What is the object weighed 600kg, what would it weigh Earth= 600 kg x 10N = 6000 kg/N Moon= 600 kg x 1.67N = 1002 kg/N Space= 600 kg x 0N = 0 kg/N Mountain= 600 kg x 9N = 5400 kg/N Is it still milk inside Is it still a litre So this states that mass stays the same If you are standing on the earth , moon and space you have the same mass but your weight changes Recap = Mass & Weight Weight Mass Measured in Newtons Measured in (N) kilograms (kg) Varies, depends on Is fixed, never where you are changes Is a force or a pull on Is a fixed property of something all things, like length or volume Calculation 3 An object of mass 50 kg has a weight of ___________ on earth 1kg = 10 N 50 kg = 500N Answer 500N Calculation 6 The mass of a man who weighs 550 N on earth is ___________ 1 kg = 10 N ? Kg = 550N Answer 55 kg Where would I weigh more? Long Jump Record Why did Bob Beaman’s 1972 long jump record (8.9 metres) last until 1991? The Olympics were held in Mexico city….he weighed less! Homework calculations 4 and 5 An astronaut has a mass of 124 kg His weight on earth is 1240 kg/N, on the moon is 207.08 kg/N and inouter space is 0 kg/N. His mass , unlike his weight never varies wherever he is Calculating Weight 5 Find the weight of a 250g bag of biscuits Solution: First change the mass to kg 250g = 0.25 kg (250g ÷ 1000) Now, F = 0.25kg * 10 m/s2 = 2.5 kg/m2 = 2.5 N