Reflection 23/08/13

This lesson in design I handed in my assignment. The past couple of lessons I have been working on my car and have been making any alterations that I think will make my car faster/quicker. I made alterations such as changing the batteries to different types, tried using different gears and lastly cutting the front of my car to different shapes to make it more streamline. A lot of these different alterations I made did make my car go quicker. Also throughout prep during the week I have been working on my assignment. I think my assignment was a bit long and I hope it is correct.

Assignment

Investigating and Designing

Friction – Define and give examples. Research aspects of friction as related to all vehicles and propose means to reduce friction when designing your vehicle.

Friction is a force that holds back the movement of a sliding object. Friction can be found anywhere where an object comes into contact with something else. Friction is the force that acts in the opposite direction to the way an object wants to slide. For example, if a car needs to stop at a stop sign, it slows because of the friction between the brakes and the wheels. Another example is if a person is running down the sidewalk and stops quickly, they can stop because of the friction between their shoes and the cement.

There are two types of friction that affect the performance of moving vehicles. These two types of friction are called static friction and kinetic friction. Static friction is the frictional force required to start an object moving on another surface. The more “stickiness” between two objects while trying to get one to move the better, but once the tires on a car start moving they do not need as great of force to continue. The second type of friction is kinetic friction. Kinetic frictional force is the force to keep the object in motion. Not only is the car making friction with the track or road, air resistance is taking place at the exact same time. The shape of any object creates air resistance when travelling at a speed. This is the pressure of the air against the car whilst it is gaining momentum; the air is then trying to slow it down.

To reduce friction whilst designing and building my car I could reduce friction by:

·       Making the car as aerodynamic as possible to reduce air resistance.

·       Make sure I have the most energy efficient wheels on my car to make sure I have a precise and effective amount of contact between the car and the road.

http://www.physics4kids.com/files/motion_friction.html

http://tristanmac.tripod.com/id13.html

Velocity – Define and give examples. Perform calculations to determine the average velocity of your vehicle

Velocity is the rate of change of an objects position with respect to time in a given direction. The units that velocity is measured are meters per second (m/s). Velocity and speed are very similar but velocity is a vector and speed is not. An example of this is suppose it was known that someone was driving at thirty-five kilometers an hour (35km/hr), but the direction wasn’t given. You wouldn’t be able to draw an arrow to draw a vector. Velocity is the rate of motion in a specific direction. Velocity can be constant, or it can change (acceleration). Speed with a direction is velocity.

V= d/t

Velocity = displacement                         Time

V= 8.75/3.18

V= 2.75 m/sec

V= d/t

V= 8.75/3.22

V= 2.72 m/sec

V= d/t

V= 8.75/3.2

V= 2.73 m/sec

Average:

A=(2.75 + 2.72 + 2.73) ÷ 3

A= 2.73 m/sec

Therefore the average velocity of my vehicle is 2.73 m/sec.

Kinetic Energy – Define and give examples. Perform calculations to determine the amount of kinetic energy your vehicle possesses as your car enters the end timing gates.

Any moving object has kinetic energy. The amount of kinetic energy an object has depends on its mass. The faster the object is travelling, the more kinetic energy it has. When an object slows down, it loses kinetic energy and when it stops it has no kinetic energy.  There are five different types of kinetic energy and these are – radiant, thermal, sound, electrical (light) and mechanical (motion).  Examples of things that have mechanical kinetic energy are things such as: wind, a flowing river, an airplane in flight, roller skating wheels while someone is skating, a car moving along a track, a child jumping on a trampoline and snow skis gliding down the mountain.

	Kinetic Energy = ½ mv2 K.E = kinetic energy (joules) m= the mass of the object (kilograms) v= the speed of the object (meters/second)

 

K.E= ½ mv²

      =  ½ x 90.9 x 2.73²

      = 338.73 joules

Therefore the Kinetic Energy of my vehicle is 338.73 joules.

http://examples.yourdictionary.com/kinetic-energy-examples.html

http://www.physics4kids.com/files/motion_velocity.html

Material	Image	Property	Uses	Characteristics
Spur Gear		Plastic	A gearwheel with teeth projecting parallel to the wheel's axis.	·       Plastic ·       White ·       Ridged ·       Circular ·       Solid ·       Rough
Pinion Gear		Plastic	Used in anything that moves along a track or to move another gear.	·       Plastic ·       White ·       Ridged ·       Circular ·       3D ·       Rough ·       Light
Axle Housings		Plastic	To protect the axel, hold it and make sure it is always able to rotate continuously.	·       Plastic ·       White ·       Circular ·       Hollow ·       Solid ·       Light
Copper Wire		Copper	To attach the vehicle to the string to guide it down the track.	·       Copper ·       Bendy ·       Light ·       Cylindrical ·       Solid
Battery Holder		Plastic, metal, wire, rubber	To hold batteries and connect the batteries to the motor.	·       Abstract Shape ·       Light ·       Plastic ·       Wire ·       Rubber ·       Black ·       Silver ·       Red
Motor		Metal	A machine, esp. one powered by electricity or internal combustion, that supplies motive power for a vehicle or for some other device	·       Metal ·       Solid ·       Abstract Shape ·       Silver ·       Black ·       Cylindrical type shape
Corflute		Corflute	To attach any the motor, switch, battery holder and axel housings to.	·       White ·       Hollow ·       Flexible ·       Light ·       Can be cut ·       Durable

Planning – A documented series of ideas showing the development of your final solution. This may include tabulated results of your testing.

To develop my ideas for my car I looked at the various ranges of cars Mr Ward had produced and listened and took notes of many of the things he said in class. If you refer to my blog http://lmcleishdf.blogspot.com.au you can see many of my ideas, notes and changes I decided to make whilst developing the idea of my car. Once I had the best information a I sat down and sketched my car. The drawing below is the only design I ever did of my car and it was a successful design as my car goes at a fast speed. I have only raced my car three times so far and they were the results I gathered to make the average velocity above. You can also see these results in the table below. I was happy with the speed my car was racing so I decided to keep it at that exact design.

Table 1: Times of recorded races.

Race	Time (sec)
1	3.18
2	3.22
3	3.2

Evaluate

Aspects of Design – Function. Based on your calculations critically evaluate your vehicle’s performance and comment on the effectiveness of your solution? What is not good or in need of attention with regard to your solution?

I think the calculations; planning and designs I made for my vehicle were very effective and did result in it having a successful performance. I think the solution I concluded with was wise and did meet the criteria and task set. The vehicle I made was very fast and that was what the aim of the assessment was.

Future improvements – State any improvements that could be made if you had the opportunity to redesign the solution i.e. ways to further eliminate friction and resistance forces.

If I were to make and design my vehicle again I would try using smaller wheels on the back but still have them a little bigger than the ones on the front. This would cause less friction with the track. I would also try and make my vehicle lighter by using less glue and maybe finding a material that is lighter than Corflute. In addition to this I would make my vehicle more streamline at the front to eliminate air resistance. Lastly, I would experiment with batteries to see which give my car the best performance.

Other vehicles: Comment on the successes and / or failures of other vehicle

Other vehicles in our class have been doing moderately well. With Alina breaking the World Record with a time of 2.48 seconds it was pretty amazing to see that the vehicles can be potentially that quick. Some girls did have struggles with making there cars run straight down the track, but I think this was due to there axles not being parallel or their guide wire touching the fishing line guide to much. Overall I think our class did exceptionally well with the majority of the vehicles succeeding on the day.