what can a force can do to an what is the unit of force? .what can a force can do to an object? 2

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  • 1. What can a force can do to an

    object?

    2. What is the unit of force?

    3. What are the different types of

    force?

  • start it moving,

    stop it moving,

    speed it up,

    slow it down,

    change its direction,

    change its shape.

  • The newton (N) is the unit of force.

    Non-contact forces include gravity

    electrostatic

    magnetism

    Contact forces include- push and pull

    friction between surfaces

    friction moving through air .

  • 1. What are balanced forces?

    2. What happens when forces act on

    a stationary object?

    a moving object?

  • 5,000N 3,000N

  • When all the forces acting on an object

    cancel each other out they are said to be

    balanced.

    When the forces on a stationary object are

    balanced, the object will not move.

    When the forces on a moving object are

    balanced the object will move at a constant

    speed.

  • 1. What are unbalanced forces?

    2. What happens when forces act on

    a stationary object?

    a moving object?

  • When the forces on an object are unbalanced

    the object will start moving and speed up.

    There is an unbalanced force on an object

    when all of the forces acting on it do not

    cancel out.

  • 1. What is friction?

    2. When is friction useful?

    3. When is friction not wanted and how can

    it be reduced?

  • Video: Friction

    Friction is the force produced when two

    surfaces rub on each other:

    The surfaces are jagged

    when observed through

    a microscope:

    This leads to friction.

    Friction song

    PULLFRICTION

    file:\\SEC-DC-001.CL15.INTERNAL\Media\SCIENCE\Friction.mpghttp://www.youtube.com/watch?v=TkXAJHitPAY&feature=related

  • Friction Both No Friction

    Ice SkatingMountain

    Climbing

    Olympic

    Swimmer

    Playing footballAirplane

    Sticking poster

    to the wall

    Walking down

    an icy street

    Throwing

    a frisbeeHorse riding

    SledgingWriting

  • Friction is the force produced when two

    surfaces rub on each other.

    Air resistance is a special kind of friction

    caused when air passes around an object.

    Friction is often useful such as allowing shoes

    to grip when walking.

    Friction can be a problem, for example when

    it opposes motion.

  • Streamlining is the process of designing the

    shape of an object so that air or water

    passes smoothly over the object so friction is

    reduced.

    Lubrication reduces friction by forcing rough

    surfaces apart and allowing them to move

    smoothly.

  • 1. What are mass and weight?

    2. How are mass and weight related?

    3. Are mass and weight the same

    everywhere?

    Video: Weighing air

    file:\\SEC-DC-001.CL15.INTERNAL\Media\PHYSICS\Weighing Air.mpg

  • Mass is the amount of matter measured in

    Kilogrammes (Kg).

    Weight is the force of gravity acting on the

    object and is measured in newtons (N).

    But how are mass and weight related?

    Lets investigate!

  • REMINDER:

    Mass is the amount of matter measured in Kilogrammes (Kg).

    Weight is the force of gravity acting on the object and is measured in newtons (N).

    Youve now found out: (note)

    Weight on Earth (N) = mass (Kg) x 10

    The 10 is called gravitational field strength or more simply, g

    But is g the same everywhere?

    Are your mass and weight the same everywhere?

  • Can we tell the weight of an

    object (in N) if we already

    know its mass (in g)?

    The mass of a convector

    heater is 3900g.

    Can you predict accurately

    the weight of the heater in

    newtons?

    clamp stand

    spring balance

    100g masses

  • Astronomers have found: the

    bigger the planets mass the

    larger is its gravitational field

    strength g !

    EARTH - 10

    JUPITER - 26

    MARS - 4

    VENUS - 9

    SATURN - 12

    URANUS - 12

    NEPTUNE - 12

    MERCURY - 4

  • Weight is the force of gravity on an object.

    Mass is a measure of the amount of matter in

    an object and is measured in kilograms.

    On the Earth the weight of an object in

    newtons is 10 times its mass in kilograms.

    The weight of an object on the Earth can be

    calculated from weight = mass x 10.

  • The force of gravity, or weight of an object is different on other bodies in the Solar System.

    Mass is the same everywhere.

    When calculating the weight of an object on other planets or moons, rather than using x10, other multipliers are used depending on the size of the planet or moon.

    Bigger planets big multiplier On Jupiter: weight = 25x mass

    Smaller planets small multiplier E.g. on Mercury: weight = 4x mass

    Now find what you would weigh on different planets and moons - research exercise,

    w/c: Gravity and the Planets

  • 1. What effect does gravity have on falling

    objects?

    2. How does friction affect falling objects?

    3. What affects the speed of a falling

    parachute?

    Video: Falling on the Moon

    file:\\SEC-DC-001.CL15.INTERNAL\Media\PHYSICS\Falling on the Moon.mpg

  • What design features of parachute affect its average speed as it falls?

    Lets investigate!

    Task:

    To make a simple parachute and to investigate how its average speed of descent depends on a chosen variable.

    Complete the worksheet as you conduct

    the experiment.

  • The force of gravity causes falling objects to

    speed up.

    When an object falls, air resistance acts

    against the force of gravity. This means the

    object will not speed up as much.

    A parachute has a large area to make the air

    friction very large so that it will balance with

    the force of gravity to allow the parachute to

    fall at a low constant speed..

  • 1. What is pressure and how is it

    calculated?

    2. What is the unit of pressure?

    3. How do changing force or area affect

    the pressure?

  • An elephant will exert less

    pressure than a person

    wearing high heels. This is

    because the weight of the

    elephant is spread over a

    larger surface area.

    Poem:

    Sir jumps quickly to his feet

    Hes got the point (-hes got a scar!)

    The pressure acting on his seat,

    Is force per unit areaaaaaaaaagh!

  • Pressure is how much force is put on a

    certain area, so

    Pressure = _______Force

    AreaN/cm2 cm2

    N

    This man can lie comfortably on the bed of nails since his weight is

    spread over many many nails.

    video: Pressure 2

    file:\\SEC-DC-001.CL15.INTERNAL\Media\SCIENCE\Pressure 2.mpg

  • For a given force, a big area means a small pressure:

    In all of these cases the pressure is smallbecause the area is big.

    The force is spread out over a bigger area so the pressure is low.

  • For a given force, a small area means a big pressure:

    In all of these cases the pressure is large because the area is small.

    The force is concentrated over a small area so the pressure is high.

  • What is the pressure of the box on the bench?

    Now try the problem sheet!

    Pressure = _______Force

    Area

    Area = 3 x 2 = 6 cm2

    = ___30

    6

    = ____5 cm2

    2cm

    3cm

    30N

    Weight of box

  • Pressure is how much force is put on a certain area.

    The unit of pressure is the newton per square centimetre (N/cm2)

    For a given force,

    a small area means a big pressure

    a big area means a small pressure

    Some practical applications of high and low pressure includes snow shoes, skis, stiletto heels, studs on football boots, spikes on running shoes, a bed of nails, camels feet

    Pressure = _______Force

    Area

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