Presentation Transcript

1. Demonstrate understanding of aspects of Mechanics

   Science 1.1 (AS09040)
2. Speed: Define the term speed Name and give symbols Use the relationship to solve problems Interpret and draw distance-time graphs Use the gradient to describe/calculate speed Specific Learning Outcomes
3. Acceleration Define acceleration and it unit and symbol Use the relationship to solve problems Draw and interpret speed-time graphs Calculate acceleration and distance from speed-time graphs Solve problems using acceleration due to gravity where g=10ms-1 Specific Learning Outcomes
4. Force Define force as a push, pull, twist or squeeze Name and give symbols of units for force and mass Give eg of contact and non-contact forces Use force diagrams Know balanced and unbalanced forces and what they do to an object Use the formula F=ma to solve problems Differentiate between mass and weight Define friction and explain how it works Specific Learning Outcomes
5. Pressure Define the term pressure including unit and symbol Use the relationship to solve problems Energy Explain that energy is need to make things happen or change Describe different forms of energy Identify energy transformations Define gravitational potential and kinetic energy with their units and symbols Use the relationships to solve problems Specific Learning Outcomes
6. Work Define the term work with units and symbols Use the relationship W=Fd to solve problems Use the relationships to determine amounts of energy transferred Power define the term power with unit and symbol Use the relationship to solve problems Specific Learning Outcomes
7. SI Units in Science
8. This sort of triangle can be useful for rearranging formula to find different aspects Cover up what it is you are wanting to find and you are left with the formula eg: Distance, Speed, Time
9. Jack wants to know how fast he can swim. What 2 measurements must he have to calculate his speed? Write down the formula for calculating speed when time and distance are known. Sam wants to know the distance she travelled to get to Masterton. What 2 measurements must she have to calculate this? Write down the formula for calculating the distance when time and speed are known. Distance, Speed, Time problems
10. Hemi wanted to know the how long took for him to get to the bus. What 2 measurements must he have to calculate the time? Write down the formula for calculating time when the distance and speed are known. Distance, Speed, Time Problems
11. Write the formula as you know it Write what you know Arrange the formula to show what you are looking for Convert what you know to the correct units Put the correct figures into the correct equation Calculate the answer Write the correct units Steps 3 and 4 you only need to do if they are needed Steps in Calculations
12. Calculate the average speed for each of the following, make sure you write down all the steps A dog runs 100m in 25s A dolphin swims 720m in 60s A car travels 227.5km in 3.5h Calculations to complete
13. Complete these questions: Isla’s scooter travels at an average of 50kmh-1. Calculate how long it will take her to travel 17 km if she does not stop. Anau is cycling at an average of 12ms-1. Calculate the distance he travels in 2 minutes Sally completes a biathlon in which she has to swim across a lake then cycle around it Calculate Sally’s speed in Kmh-1 for the swim Calculate Sally’s average speed for the entire race Calculations to complete
14. Distance-time graphs 1
15. Distance-time graphs 2
16. After 1s, what distance from the start was the object represented by line A Calculate the speed of this object From the graph, state the total number of sec the moving object in line B was: Moving:_______ Stationary: _________ Distance-time graph problems 1
17. Students carrying a stopwatch stood every 20m along a 100m track. They started their timer when a cyclist started moving, then stopped it when the cyclist passed their position. Here are the results: Draw a distance time graph of these results Describe the motion during the first 60m Describe the motion between 60m and 100m Distance-time graph problems 2
18. The distance-time graph for a dog chasing a stick is below: Use the graph to answer the following questions: Calculate the dog’s speed for the first 12s What was the dog’s speed during the time 12-18s Describe the motion of the dog from the time 18-36s Distance-time graph problems 3
19. A ticker timer can be used to record the distance and time information for a moving object. This can then be used to calculate speed Eg on the next slide is a ticker timer tape collected when a trolley with the tape was rolled along the bench. We know that every 10 dots is 0.2 s and we can measure the distance between each of these and use this to calculate the speed Ticker timers and speed
20. 0 0 1.5/0.2 =7.5 1.5/0.2 =7.5 4.5/0.4 = 11.5 3.1/0.2 =15.5 6.4/0.2 32 11.0/0.6 = 18.3 Ticker timers and speed 2
21. As with the speed formula, the acceleration formula of: can also be put into a triangle to rearrange it and solve different problems Acceleration
22. Complete the table by calculating the different values: 2.25 3.7 1350 63 4.3 8.3 Acceleration problems
23. Speed-time graphs
24. Look at this graph of a bus journey: What was the speed of the bus at 3.5s? How long did it take the bus to reach a constant speed? Work out the acceleration of the bus in ms-2 over the first 3s. What is happening to the bus over the last 2.5s of its journey? Use the graph to work out the total distance travelled during the journey Speed-time graphs 2
25. Forces are pushes or pulls and change the shape, speed and direction of an object They can be contact or non-contact Forces have a size and direction The net force of an object is calculated when all of the forces acting on an object are totalled. If the net force is zero the forces are said to be balanced If the net force if great in one direction, they are not balanced Force, Mass and Acceleration
26. If the opposing forces are balanced there is no net movement If one force is bigger than the other the object will move in that direction Weight Thrust Drag/Friction Thrust Support Force, mass and acceleration 2
27. The formula F=ma can be used to show the relationship between these things where: F = force (N) m = mass (kg) a = acceleration (ms-2) The triangle can also be used to rearrange this formula There are 2 patterns to remember: Greater force = greater acceleration Larger mass = smaller acceleration Force mass and acceleration 3
28. In the following situations the net force on the object is known. Write down the size of the forces A-D Roger Federer can hit a tennis ball (0.057kg) so the ball accelerates at 224ms-1. Calculate the force the racquet exerts on the ball A box is dragged across an icy surface with a force of 47N. It is accelerating at 0.08ms-1. Calculate the mass of the box Force, mass and acceleration problems
29. Mass is the amount of matter an object has Gravity is the force pulling an object to another. On earth this is approx. 10ms-2 Weight is the effect of gravity on an object and is a force (N) The formula to calculate weight is: Fw = mg (where g=10 on earth) Mass, gravity and weight
30. Friction is a force created when 2 surfaces move, or try to move across each other. It opposes the movement of one object past another Copy and complete the following paragraph: Friction is a ________ that is created when two ______ move or try to move. Friction acts in the ______ direction to movement and depends on the ______ of the two surfaces. Friction can be useful eg ______ slow down a car, or not useful eg rubber wearing off a ____. Wheels reduce friction by ______ the areas in contact. The friction that prevents a stationary object from moving is _____ friction. The friction force or air is also known as _____. Friction
31. Pressure depends on two things Force applied Area being pushed on The relationship is: A force acting over a small area gives a larger pressure than the same force acting on a larger area The trick with these questions is to make sure you look at the whole area (ie is there 1 shoe or 2, are there studs and how many) Pressure
32. The diagram below shows a pair of ski’s. Calculate the pressure exerted when Rosemary (60kg) stands upright on these ski’s Pressure question
33. Energy is required to make anything happen or change There are different forms of energy potential (stored) energy and other active forms: Heat Sound Solar Kinetic (the energy of a moving object) Gravitational potential Elastic potential Chemical Potential Energy 1
34. The law of conservation of energy states that: “energy cannot be created nor destroyed, merely changed from one form to another”. This is an energy transformation and is usually shown as below: Chemical potential Elastic potential Kinetic gravitational potential kinetic Energy 2
35. The formula for this relationship is as follows: Ep = mgh Ep is Potential energy m is mass g is gravity (10) h height (of object off ground) A 900kg car is lifted 2m above a workshop floor. How much Gravitational potential energy does it have? Ep=mgh where m=900, g=10, h=2 Ep = 900 x 10 x 2 Ep = 18000J Gravitational potential energy
36. The formula for the energy of a moving object is as follows: Ek = ½mv2 Ek is energy in J m is mass in kg v is velocity in ms-1 A 1000kg speedboat is travelling at 16ms-1 How much energy does it have? Ek= ½mv2 where m=1000 v=16 Ek = 0.5 x 1000 x 162 Ek = 128J Kinetic energy
37. Usually kinetic energy comes from potential energy For some excellence level questions you have to calculate the amount of potential energy then use this figure to calculate the speed of an object by rearranging the formula In this case you have to assume that all of the potential energy is converted to kinetic energy with none being lost Potential energy into kinetic energy
38. Eg; A sack with a mass of 50kg is raised to a height or 5m above the ground and is allowed to fall. What is the sacks gravitational potential energy before it is released? How much speed does the sack have just before it hits the ground? However we know that some of the energy is always lost as ______ Potential energy into kinetic energy 2
39. In order for energy to change from one form to another, work must be done. The relationship for this is: W = Fd W is work (J) F is force (N) d is distance (m) This can also be put into the triangle as the formulae earlier in order to calculate any part of it Work
40. Complete the following table: Calculate the work done when a person uses a constant force of 25N to drag a box for a distance of 15m You should be able to see that the amount of energy that is required to move that box will be the same Yes Movement against the main opposing force of friction of the floor No No movement Work done in the change of Gravitational potential energy to kinetic energy Yes Work problems
41. Power is the rate at which work is done It uses the formula Usually a question will ask you to compare two things and say which was more powerful and why Two men were bench pressing 80kg (pushing the weights upwards from their chest as far as their arms could extend). One man’s arms were 0.65 m long and the other man’s were 0.60 m long. Both men took exactly 2.5 seconds to fully extend their arms. The man with the longer arms said that he had to do more work than the man with the shorter arms but the man with the shorter arms was more powerful. Was he correct? Power