Transcript Mass and Weight

Thursday 21st June 2012
Physics: Transport Homework 1
Measuring Forces
A force is something that can change the
SPEED , DIRECTION or SHAPE of an object.
Forces are measured in NEWTONS (N).
The size of a force can be measured with a
Newton Balance.
The Force of Gravity
Everyone knows that when we let things go they
always fall down – never up!!
Sir Isaac Newton was the scientist who wondered
why things always fall down. He decided there must
be a force doing this ‘pulling’ – he called this force
GRAVITY.
All objects produce a force of gravity. However
only massive objects like planets and the Sun
produce strong enough forces for them to be
noticed. The bigger the object the bigger the
force of gravity!!
Sir Isaac Newton showed that the force of gravity
from the Sun keeps the Earth in orbit (it is like an
invisible string between the Sun and the Earth)
and similarly Earth’s gravity ‘holds’ the moon.
The force of gravity on any object is actually the
weight of the object!
So this means that because weight is a force it
is measured in NEWTONS!
The thing we usually call ‘weight’ and is
measured in kilograms and grams is really
called the MASS!
Mass and Weight
The mass of an object tells us how much ‘stuff’ is
in it. It is also to do with the number of particles
that make up the object.
Mass is measured in kilograms ( and sometimes
grams, tons etc.)
Weight is measured in Newtons.
Mass and Weight Experiment
AIM: To find out if there is a connection between
mass and weight.
METHOD:
Use a Newton Balance to
measure the force of
Gravity (weight) on
different masses.
RESULTS:
Mass (kg)
Weight (N)
0.2
0.4
0.6
0.8
1.0
My mass
My weight
CONCLUSION: The weight of things on Earth is
10
_______
times the mass in kg.
10
Every kilogram on Earth has a weight of _____N.
“Show Me” RECAP
70kg
Earth
g = 10N/kg
Zelda
g = 2N/kg