Cars And Forces - Gravity

What happened before Isaac Newton invented gravity? Non Contact Forces To be able to: All Most Some Say what is meant by gravity (Level 4) Give examples of forces that don’t need objects to touch (level 5) Explain the difference between mass and weight (Level 6) Levels of Learning At which students are required to demonstrate their ability Associated action verbs Knowledge to recall a wide range of knowledge, facts and experiencesdescribe, recall, define, state, recognise, name, list, underline, reproduce, measure, write, label, identify, acquire Comprehension to grasp the meaning of their acquired knowledge, and to process, translate and interpret this knowledgecomprehend, understand, draw, interpolate, extrapolate, predict, to have insight into, translate, illustrate Application to apply knowledge and comprehension in different situations, relate material, and infer from factsapply, show, demonstrate, perform, use, relate, develop, transfer, infer, construct, explain Analysis to analyse data or material, breaking it down into its component parts so that its organisational structure may be understoodanalyse, identify, separate, detect, break down, discriminate, categorise, distinguish Synthesis to synthesise and combine elements to produce a coherent whole and make logical deductionscombine, restate, summarise, précis, generalise, conclude, derive, organise, design, deduce, classify, formulate, propose Evaluation to evaluate data, make judgements and assess materialevaluate, judge, decide, choose, assess, contrast, criticise,select, defend support, attack, seek out, compare, determine. Starter – List all the things that a force could do to a ball

Why did the ball fall down? Why does rain always fall downwards towards the Earth? Why doesn’t water come out of the tap sideways? Why don’t people on the other side of the Earth fall off into outer space?

The answer to all these questions is the force called… gravity

The larger the mass of an object, the larger the force of gravity. What is Gravity? Gravity is a force (gravitational force) that acts on all objects on earth. This force holds the Earth (and the other planets) in orbit around the sun and the moon around the Earth and satellites in orbit around the Earth.   The larger the mass of an object, the larger the force of gravity.

Gravity- recap The force of GRAVITY is what keeps us on the SURFACE of the EARTH. You do not have to be TOUCHING the Earth to feel the force of gravity. GRAVITY ON EARTH PULLS YOU DOWN. GRAVITY ALWAYS PULLS; IT NEVER PUSHES. We can draw an arrow on the shark and car to show the direction of gravity:

Do you know what we call this force? Upwards Forces I If there is a downwards force of gravity pulling on a car then why does it not get pulled into the ground? Reaction There must be a force PUSHING UP on the car that stops it getting pulled into the ground. Gravity Do you know what we call this force? The REACTION FORCE.

Do you know what we call this force? Upwards Forces II If there is the downwards force of gravity pulling down on a floating shark then why does it not sink deeper into water? Upthrust There must be a force PUSHING UP on the shark that stops it getting pulled further down. Gravity Do you know what we call this force? The UPTHRUST.

Force Diagrams exercise Label the forces acting on a rocket moving through the Earth’s atmosphere. Upthrust Air resistance Gravity Thrust

Force Diagrams Exercise Label the forces acting on the shark. Upthrust Thrust Friction Gravity

What could force do to a ball? Remember, forces can be: Push Pull Twist Do things have to touch for forces to work?

Weight – What is weight? The pulling force of gravity always acts towards the centre of the Earth, wherever you are on the planet.

The effect of the force of gravity on an object is called the object’s… weight Weight is a force and is measured in Newtons. Why is weight different to mass?

Mass – What is mass? The amount of material in an object.   MASS is the resistance to a change in the motion of a body. Mass remains constant anywhere in the universe. Weight does not remain constant anywhere in the universe.

The girl below is not moving. Are there any forces acting on her? An upwards force is produced by the chair in the opposite direction to gravity. The girl’s weight due to the force of gravity is pulling her mass down on the chair. The girl does not move because these forces are balanced. What does this tell you about the size of these forces? Draw five examples of balanced forces.

Practical Hang a holder from the spring balance. Find a mass. What is its mass in Kg (1000g = ??kg) Add it to the holder. Read the weight on the spring balance. Record your results in a table.

Gravity changes depending on where you are in the Universe. What happens to weight and mass when gravity changes?   Our friendly alien Ms. A Lean will help you find out more…

On Earth, a mass of 1 kg has a weight of 10 N. My mass is 42 kg. What is my weight on Earth?

The force of gravity on the Moon is 6 times less than on Earth. My mass is still 42 kg. What is my weight on the Moon?

My weight in outer space is 0 N. In outer space, far away from any planets or stars, there is no gravity pulling on me. My weight in outer space is 0 N. What is my mass in outer space?

Look at Concept Cartoon 11.7 Testing our Knowledge Look at Concept Cartoon 11.7 What do you think?

Gravity Poem Working in pairs… write a 5-line poem about Gravity Line 1 is one word – it’s the KEY ISSUE for today - GRAVITY Line 2 is two words and describes what the first line MEANS Line 3 is three words and describes what the first line DOES Line 4 is four words - say what the first line MEANS TO YOU Line 5 is one word and says the first line using ANOTHER WORD Example DISSOLVING break apart makes pieces smaller solid mixes with liquid PHYSICAL

Homework You will explain what you have learned in these three lessons to someone at home. Write down 5 bullet points to help you (I want to see those bullet points!). Do they have any comments or questions? If so, write them down.

Non-Contact Forces Learning Objectives To be able to: Give examples of forces which don’t need objects to be in contact Explain the difference between mass and weight How is gravity like magnetism … and how is it different to friction?

Look at the table. What does it tell you? Starter thinking skills Look at the table. What does it tell you?

Tables present data, helping us to answer questions and see patterns in results. What questions could you ask about this table that others in your class could answer?

Questions 1. The lift in a tall building hangs from a strong cable. The movement of the lift is affected by only two forces. These forces are the tension in the cable and the weight of the lift. (a) The lift is not moving. How do the sizes of the two forces compare? (b) When the lift is moving upwards and its speed is increasing, how do the sizes of the two forces compare? (c) When the lift is moving upwards at a constant speed, how do the sizes of the two forces compare? (d) Near the top of the building the lift is moving upwards, but slowing down. How do the sizes of the two forces now compare? w e i g h t c a b l n s o f

Assessing what we have learned Learning Objectives To be able to: Identify what we have learned so far in this topic Did you have any surprises in the work you did today?