4-FAD-01

Outcomes

• Pupils can arrange all the GCSE quantities into two groups: scalars and vectors.
• Pupils appreciate that force is a vector quantity and understand the nature of this.
• Pupils can name and label forces on stationary objects using arrows (1-D) and show that they are balanced.
• Pupils can add force vectors that act along a line.

Specification References

• 1.10 distinguish between vector and scalar quantities
• 1.11 appreciate the vector nature of a force
• 1.12 add forces that act along a line

Starter

• Introducing the idea of vectors to the class. Here are two options.
• 1) Begin by telling the class "A bag of gold is located outside the classroom. To find it, displace yourself 20 meters." Encourage the students to discuss your statement. Is there enough information included in the statement to find the bag of gold? The displacement required to find the bag of gold has not been fully described. Now, tell them "A bag of gold is located outside the classroom. To find it, displace yourself from the center of the classroom door 20 meters in a direction 30 degrees to the west of north." This statement now provides a complete description of the displacement vector - it lists both magnitude (20 meters) and direction (30 degrees to the west of north) relative to a reference or starting position (the center of the classroom door). Vector quantities are not fully described unless both magnitude and direction are listed.
• 2) Ask the pupils to estimate the number of steps needed to reach the back of the classroom. Once you have an agreed number of steps from the class begin walking to the back of the room (counting the number of steps as you go along) but walk in and out of the desks. Question how the pupils could have gotten it so wrong and begin to introduce the terms distance and displacement and how vector quantities are not fully described unless both magnitude and direction are given.
• Next, split the class into groups of six and give each group a pack of cards which contain all the GCSE quantities. Ask them to divide them into two groups: 1) those that have a direction and can be represented with an arrow (a vector) and 2) those that do not (a scalar).
• These cards should be left while they carry out work on the force table.

Main Body of Lesson

• The groups of six can be split into groups of two to investigate vectors on the force tables. They can work through this force table work sheet where they are asked to apply different arrangements of masses/forces pulling on a central block. They are asked to make and record a prediction before releasing the block and also to record their observations.
• Regroup them and ask them to discuss the observations and write their own definition for a vector and scalar quantity on the mini whiteboards.
• Discuss the groups outcomes and write defintions for vectors and scalars to be recorded in their books. Emphasise that vector quantities could be negative whereas scalar quantities cannot. (They may argue about temperature where they can be introduced to the Kelvin scale)
• The groups will reassess their vector and scalar groups after the powerpoint.
• Use the Force vectors powerpoint. Discuss the images and have the class help label the forces using arrows. Guide them towards the correct direction of arrow and type of force as revision from the 3rd year. Begin looking for pairs of forces which are balanced and result in zero force on the object.
• Explain that force vectors are depicted as arrows to show the direction, with the length of the arrow representing the magnitude of the force. You could introduce the 'head' and 'tail' of the force vector.
• Use the last few images (the canal boat and the loop) in the powerpoint to introduce the idea that the resultant of two given forces is an imaginary force and is equivalent to the actual forces. It would have the same effect as the real forces combined.
• Go through the examples on how to add vectors from the power point slide. Emphasis how to add vectors 'head to tail'. Make them redraw the arrows in 'head to tail' formation.
• ==REGROUP== Have the groups reassess their vector and scalar groups from the beginning of the lesson and make any corrections they feel they need to make.
• Make a centralised list on the board and have them copy this under their defintions in their books.
• ==EXTENSION== If there is time and you wish to extend to 2-D vectors a nice activity is to use the trio of ropes tied to a loop. In groups of four, have three pupils pull on the three ropes using forcemeters. They should pull and create a 'balanced loop' which is resting on the A3 paper. The fourth member uses a ruler to trace the three ropes with a pencil (on both sides) and label the force from the forcemeter. The centre of the loop should also be marked. Now have them take the loop and rope away and using the pencil draw the force vectors leading from the centre of the loop. The vectors should be in the correct direction and be drawn to scale. (i.e 2cm = 1N) Now using the acetate sheet they should trace the vectors one at a time 'adding them' head to tail. (They will get the direction correct if they concentrate on keeping the same acetate edge parallel with the same paper edge. The three force vectors should create a triangle showing that they are balanced or the resultant is zero.

Plenary

• Vector Addition Game
• Supply the pupils with large squared paper with the same starting point and end point labelled.

Homework

• Use this Adding Forces sheet. Student should add forces along a line and may go onto an extension activity where they both label and add up forces for a number of situations.
• Students could research the difference between speed and velocity and how the change in velocity can occur by the velocity only changing direction and not magnitude. This could lead them to the idea of circular motion.

Additional Information

Resources Required

• Class set of quantity cards in envelopes + whiteboards
• Force tables - boards x 12, bull dog clips with one lever bent upward x 48, string, block with four eyelets at the centre of each side, 100g mass sets, deep plastic trays x 24
• Set of 'ring with three ropes' systems, 3 Newton meters x 3, A3 sheet x 1, acetate sheet x 1 , rulers x 1 and OHP pen x 1.

Textbook References

• None

Website References

• None

Safety/Hazards

• None

Notes

• None