Forces in Action

There are many different types of forces. Some of these we encounter every day (but we probably don’t think about them much) whilst others take a bit of noticing.

Over the next few weeks we are going to investigate forces. You will do a series of practical activities and a range of questions. Then you will go on to design and complete your own practical investigation related to forces.

You will need to work in groups to complete these tasks BUT EVERYONE MUST COMPLETE THE WRITTEN WORK IN THEIR OWN WORKBOOK. You may need to finish some of these tasks at home.

The assessment for this unit will be based on 3 tasks.  Completion of Activity Booklet 30%  Practical Investigation Report 30%  Topic Test 40%

Make sure you ask your teacher if you need help.

May the Force be with you!

1 On The Move

Activity 1: What Can A Force Do?

Complete Activity 1 and write your answers in the space below Observations What To Do Are there changes in Shape or What caused the change Motion Stretch a rubber band Squash a lump of plasticine Push down on the floor with one foot Drop a tennis ball. Observe what happens (a) at the moment that you drop it (b) as it falls (c) as it hits the ground (d) as it goes up again Flick a coin with one finger so that slides along the surface of a table. Observe what happens after the coin is flicked.

Activity Questions 1: When you squash a lump of plasticine and stretch a rubber band a change of behaviour is observed. What is different about the behaviour of these 2 materials?

2: Does the tennis ball change its shape when it hits the ground? What will happen to a falling lump of plasticine when it hits the ground? Check your prediction. Can you change its shape to make it bounce?

http://en.wikibooks.org/wiki/FHSST_Physics_Forces:What_is_a_force

Question 1: What is a force?

Question 2: What can a force do?

Question 3: What unit is force measured in? (for example, the unit for distance is metres) Electrostatic Force (An Example of a Non-Contact Force) Activity 2: Electrostatic Forces Complete the tasks below and record your results in the space provided Task Observations Explain What You Think Is Happening

Teacher demonstration of the Van de Graaf Generator (1)

Teacher demonstration of the Van de Graaf Generator (2)

Charge a plastic ruler or rod by rubbing it with a nylon or wool cloth – use it to pick up small pieces of paper

Charge a plastic ruler or rod by rubbing it with a nylon or wool cloth – hold it close to a thin stream of tap water

Question 1: What is static electricity?

Question 2: What are the laws of electrostatics?

Question 3: Why might 2 objects that have electrostatic charges on them move away from each other?

3 What’s The Attraction?

Activity 3: What Does A Magnet Attract? Complete Activity 3 and write your answers in the space below. Attracted Not Attracted Questions 1: Which materials were attracted to the magnet?

2: Which material was MOST attracted to the magnet? Why do you think this is?

3: What types of substances appear to be affected by the magnetic force?

Activity 4: Magnets, Magnets and More Magnets

Complete Activity 4 and write your answers to the questions in the space below. A: Why do you think each of the paperclips is attracted to the one above?

B: What happens when the second paperclip is separated from the first?

C: What happens to the other paperclips? Why?

4 Activity 5: Poles Apart

Complete Activity 5 and write your answers to the questions in the space below. Like Poles …..

Unlike Poles ….

Question 1: What is a temporary magnet?

Question 2: What is a permanent magnet?

Question 3: What are the names given to the 2 ends of a magnet?

Question 4: Natural permanent magnets contain at least one of several elements which make them naturally magnetic. What are the names of these elements?

Activity 6: Making Your Own Compass

Complete Activity 6 and write your answers to the questions in the space below.

1: Is your magnet a permanent or temporary magnet?

2: Which end of your magnet is the north pole? How do you know?

5 Invisible Forces

Question 1: What is a magnetic field?

Activity 7: Mapping the Magnetic Field? Complete the Activity below and write your answers in the space provided. In this task you will use magnets to investigate magnetic field lines. When you place a magnet (or magnets) or top of the iron filings (which are held in the flat white containers) a pattern will be created. You may need to tap the container very lightly to help. The pattern that is created is a map of the magnetic field around the magnet. The magnetic field is strongest in places where there are a lot of iron filings. 1: Which part of a bar magnet has the strongest magnetic field? How do you know this?

2: What happens to the strength of a magnetic field as it gets further away from the magnet?

3: Draw a diagram of the magnetic field around a bar magnet.

4: Place a small compass at several places around the magnet. The direction the compass points shows the direction of the field. Add arrows to the diagram above to show the magnetic field direction.

5: Investigate and then draw diagrams of the field lines around the following magnets.

6 Research Task: Select at least 3 of these tasks.

1: How does a compass work?

2: Magnets and compasses do not point exactly to the magnetic north pole. Find out where the current magnetic north pole is and also whether its position is stationary.

3: Why is the earth’s magnetic field so important to us? What does it protect us from?

4: What are the Auroras or the Northern and Southern Lights? What do they have to do with the Earth’s magnetic field?

5: The Earth’s magnetic field sometimes flips from North to South. Find out about this process. When did it last happen? When might it happen next? How do scientists know?

7 Switched on Magnets

Activity 8: Making an Electromagnet? Complete Activity 8 and write your answers in the space below. Number of Number of Windings Paperclips Questions to Answer 5 1: What is the effect of increasing the number of windings on the nail? 10

15 2: What is the effect of increasing the voltage?

25 3: In your own words explain how your electromagnet works.

Question 1: What is an electromagnet?

Question 2: What are the key parts of an electromagnet?

Question 3: What do you think happens to the magnetic field of the magnet when the electricity flow (the current) changes direction? Can you test this?

8 Walking On Water

Activity 9: Are Things Really Lighter in Water Complete Activity 9 and write your answers in the space below. 1: Does the stone feel any lighter?

2: Use a spring balance to find the weight in Newtons of the 500g mass before placing it in the water. Weight = ………Newtons

3: Now place the mass in the water and record the reading on the spring balance. Weight = ………Newtons

4: The difference between these values is how much the water supports the mass (or the force of the water on the mass). We Buoyancy Force = ……N call this the Buoyancy Force. Determine the buoyancy force. 5: Is the 500g mass really ‘lighter’ when it is in the water?

Activity 10: Holding It All Together Complete Activity 10 and write your answers in the space below. Number of Water Drops on a 5 cent piece = 1: Describe the shape the water makes as you add it to the 5 cent piece.

2: What seems to keep the water on the coin?

3: What difference does adding detergent make to your result?

Question 1: Are buoyancy and surface tension the same thing? Explain.

9 Friction – Friend or Foe?

Activity 11: Measuring Friction Complete Activity 11 and write your answers in the space below. Force of friction (Newtons) Trial Surface 1 2 3 Average

Activity Questions 1: List the surfaces in order from the greatest friction force to the least.

2: What feature of the surface seems to determine the amount of friction?

3: Why was it a good idea to repeat each measurement 3 times?

Question 1: What is the force of friction? Why does it occur?

Question 2: Try the online experiment at http://www.fearofphysics.com/Friction/friction.html Change the friction the truck experiences by altering the road condition (Try dry road, wet road, icy road). What occurs as the friction between the wheels and the road changes?

Question 3: Why would life be difficult if we didn’t have friction?

10 An Attraction to the Earth

Activity 12: Web Task Have a look at http://www.exploratorium.edu/ronh/weight/

What would your weight be on: Mercury

The Moon

Jupiter

A Neutron Star

1: Would your mass (that is – the amount of ‘stuff’ in you) change at each of these locations?

2: What does the mass of an object depend on? (Also read the information below)

3: What does the mass of an object depend on? (Also read the information below)

Mass vs. Weight

The force of gravity is a source of much confusion to many students of physics. Mass is related to "how much stuff is there" and weight is related to the pull of the Earth (or any other planet) upon that stuff.

The mass of an object (measured in kg) will be the same no matter where in the universe that object is located. Mass is never altered by location, the pull of gravity, speed or even the existence of other forces. For example, a 2-kg object will have a mass of 2 kg whether it is located on Earth, on the moon, or on Jupiter;

On the other hand, the weight of an object (measured in Newtons) will vary according to where in the universe the object is. Weight depends upon which planet is exerting the force and the distance the object is from the planet. Weight, which is the same as ‘the force of gravity’, depends on the value of g (acceleration of gravity) the object is experiencing. On Earth's surface, g is often approximated to 10 m/s2. On the moon's surface, g is 1.7 m/s2. So g on earth is about 5 times greater than the value for g on the moon. This means that things on earth are about 5 times heavier compared to the moon. (Even though their mass would be the same)

11 Falling Down

Activity 13: More than One Force

Complete Activity 13 and write your answers in the space below.

1: How many forces are acting on the coin as it falls through the air?

2: Which object (paper or coin) landed first?

3: What 2 forces were acting on the paper disc?

4: What is different about the forces acting on the coin compared to the forces acting on the paper?

5: Place the disc on top of the coin and drop them together from waist height. Which lands first? Why do you think this has occurred?

Question 1: Explain what air resistance is.

Question 2: Explain what terminal velocity means.

Personal Investigation Into Forces 12 This part of the task requires you to undertake your own investigation related to forces. You will need to design an experiment, check it with your teacher, undertake a risk review, write up an equipment list, complete the experiment and then write up a report.

The aim of any experiment is to try and find something out (we call this drawing conclusions). To make valid conclusions you need to make sure that your experiment is well controlled. In any experiment you should try to change only one thing at a time and keep everything else constant. All the things that can be change are called VARIABLES. So only one variable should change at a time – this is called the EXPERIMENTAL VARIABLE. All the other variables are the CONTROLLED VARIABLES.

The results you get are called your Data. You should try to put your data into a table. The headings for the columns in your table are normally the names of the variables. Your data might also be graphed.

Your Report needs to follow the standard report format. Refer to Page 18 of your text and follow this.

Possible Topics 1: Investigating Parachutes Design a parachute and find out the effect that changing one of the following factors has on its performance – the mass of the skydiver, the area of the parachute, the shape of the parachute.

2: Crash Test Dummies Use a crash test dummy made of plasticine to investigate what occurs in a head on collision. Modify the experiment to make use of different materials as crumple zones.

3: Egghead: Modelling Bicycle Helmets Design, build and test a container that will protect a hardboiled egg from cracking when dropped from a height of 1.5m. Investigate the use of different materials in your design.

4: Electrostatics and Electroscopes Find out what an electroscope is and then build one. Test the electroscope and modify it with improvements.

5: Floating Bodies Design an experiment to investigate Archimedes Law of Buoyancy. Perhaps consider varying the shape of an object and determine the impact shape has on the buoyancy force.

6: Investigating Surface Tension Design an experiment to investigate the surface tension of different fluids.

7. An experiment of your own design