Chapter Challenge

1. Chapter Challenge Tetsuji OnoJulia EisenMaria Enokian

2. Section 1 • Reaction time is the amount of time that it takes someone to react to his or her surroundings. There can be many distractions that can slow down one’s reaction time while driving. These distractions include: o Typing a phone number o Changing a CD o Eating food o Smoking o Playing with a laptop o Reading a book o Dancing o Taking care of kids o Emotions o Talking to someone in the carIn addition to distractions effecting reaction time, drinking alcoholic beverages or taking drugs also greatly affects reaction time. Having these substances inside of your body while you are driving can cause you to have a slower reaction time in addition to having worse judgment while on the road.

3. Section 1 Cont. • Other factors that can affect reaction times are:Being tiredAgeGenderBeing under the influence of alcohol or drugs, being distracted, or any of the above factors greatly affects one’s driving and his reaction time.Having a faster reaction time would be better for any driver because if someone has a faster reaction time, he can react to a situation more quickly, ultimately avoiding a collision or accident. If someone has a slow reaction time, then he will react to a situation slowly and may not be able to avoid getting into a collision and it may be dangerous for him and the people around him.Although teenagers generally have good reaction times, the reason that insurance for them is higher than that of older people is because teenagers do not have as much experience as older people do and the teenagers may get more distracted than the older people will. 

4. Section 2 • Random and Systematic Errors:There are two different kinds of errors that can be made in measurements. The first kind is random errors. Random errors are when someone rounds incorrectly or when he does not measure correctly. A systematic error is one where the way that someone makes an error in a measurement is by using the wrong measurement such as inches instead of centimeters or by using a yard stick consecutively and not realizing that the stick is missing two of its inches.Accuracy and Precision:Accuracy is when you are close to the correct answer. Precision is where all of the measurements that you take are close to each other. You do not need to be accurate to be precise. For example, if you measure something five times, but all of those five times you made the same error, then your answers would be precise. You also don’t need to be precise to be accurate because you could measure five times and get only one of your answers accurate to the correct answer.You need to know about measurements in driving because when you are driving, you need to estimate the amount of space in between your own car and another car. Based off of these measurements, you would be able to estimate the amount of time that you have to turn or to start or stop.SI unit and conversion:Kilograms • Meters • Seconds • Distance Formula:V=d/t(Velocity= distance divided by time)

5. Yellow Lights • Yellow Light Analysis • Yellow lights do not have a fixed amount of time in which they stay yellow. They vary, and some can be 3 seconds and others 6 seconds. • In a road, there is always a Go Zone and a Stop Zone. They indicate whether you should go or stop when you approach a yellow light. • Go Zone equation is C4*C2-C6. C2 is the yellow light time. C4 is the speed of the vehicle. C6 is the width of the intersection. Although when you look at the yellow light model there are other variables. Those do not affect the Go Zone but the Stop Zone. • Yellow light time effects the Go Zone because you need to know how much time you have to cross the intersection. • The width of the intersection affects the Go Zone because you need to make sure to input that with the distance you are away. Not good if you end up in the middle of the road. • The speed at which you are going also affects the Go Zone because if you are going faster, there is an increase of the Go Zone. But you need to be careful since if you increase speed, it decreases overlap, and could end up creating a dilemma zone. • Dilemma zone is the place in the road at which if the light turns yellow, you cannot go or stop. This is because both would be dangerous. In order to eliminate dilemma zones, yellow light time should be increased. • Overlap zone is the zone at which you can go or stop. Both are safe to do. It’s good to have an overlap zone because this way, drivers who are making a decision to go or stop can choose either.

6. Yellow lights CONT!. • The Stop Zone equation is C4*C3+C4^2/(2*C5). As you can see, the factors that affect Stop Zone are not the same at the factors that affect Go Zone. But there is one similarity. Go Zone and Stop Zone are both affected by the speed of the vehicle which is C4. In Stop Zone you need to know the speed of the vehicle because the faster you are going, the smaller the Stop Zone will get since you cannot stop in time. C3 is human response time, which you need when you are stopping. When the light turns yellow, and your reaction is slow, you may not be able to stop in time. If your reaction is fast, you will be able to stop in time. C5 is negative acceleration. This is the speed at which your car is slowing down. Negative acceleration is calculated by the amount of friction and the speed at which you are going. Also if you have bad brakes, your negative acceleration may be slower. • In order to calculate dilemma and stop zone, you use this equation. Go Zone – Stop Zone. If your result for it is greater than zero, than you have an overlap. If it is less than zero then you have a dilemma. • To sum up, the factors which affect if you should go or stop are • Yellow light time • Human response time • Speed of vehicle • Negative Acceleration • Width of Intersection

7. Speed, Friction and the Radius of a Curve • When you are in a car, and you turn, you usually feel as if some force is pushing you in the different direction than you are going. For example, when you turn left in a car, you sway to the right. But actually, there is no force, it is just inertia. Inertia is the property of matter that resists changes in motion. This is measured with mass. • The acceleration on a curve can be shown with the equation Ac=v^2/r • The velocity squared divided by the radius. Ac is directly proportional to the velocity because as velocity increases, the acceleration also needs to increase in order to keep the circular motion. It is inversely related to the radius because, as the radius increases, there is circular distance is greater so the acceleration needs to decrease in order to keep the circular motion.

8. Speed, Friction and the Radius of a Curve Cont. • In the chart above, B shows the correct motion in which a vehicle would go through when being pulled by a sting in one point and is released. This is because when the string is released, the force or acceleration is suddenly gone, and the only motion is the velocity tangent to the force or acceleration of tension. • Centripetal force – the force perpendicular to velocity. Always points to the center. • A force is a push or pull which is external to the object. • The 4 types of forces are tension, weight, friction and normal. • Tension is the force on the string. • Weight is the force of gravity. • Friction is the force between two surfaces. • Normal is the force of another object perpendicular to the surface. • Law of Inertia – An object in motion tends to stay in motion. This is in constant speed and direction. The same as an object at rest tend to stay at rest. • This cannot be seen on earth because the force of gravity and friction always applies on everything. • Newton’s Second Law • Force needed to accelerate a mass is directly proportional to the acceleration. Total F = ma • F is the force. m is the mass. a is the acceleration. • The coefficient of friction can be written as µ. • In normal circumstances 0< µ<1. The equation for friction can be written as f = µ * FN • In level surfaces it is f = µ * mg.

9. Negative Acceleration • Negative acceleration: a change in the velocity with respect to time of an object by decreasing speed in the positive direction or increasing speed in the negative direction.

10. Average Speed: Following Distance and Models of Motion • speed: the distance the distance traveled per unit time. Speed is a scalar quantity, it has no direction. • constant speed: speed that does not change over a period of time. • average speed: the total distance traveled divided by the time • instantaneous speed: the speed at a given moment. • velocity: the speed in a given direction. • reaction distance: the distance that a vehicle travels in the time it takes the driver to react. • Doppler effect: the change in the pitch, or frequency of a sound (or the frequency of a wave) for an observer that is moving relative to the source of the sound (or source of the wave). • You saw that when an object is moving at a slow speed, the distance between the objects is less than when the object is moving at a fast speed. This makes sense, because at a slow speed, the object travels a shorter distance during the same time than at a fast speed.

11. Graphing Motion, Distance, Velocity, and Acceleration • acceleration: the change in velocity with respect to achange in time. • vector: a quantity that has both magnitude and direction. • negative acceleration: a decrease in velocity with respect to time.The object can slow down (20 m/s to 10 m/s) or speed up (-20 m/s to -30 m/s). • positive acceleration: an increase in velocity with respect to time. The object can speed up (20 m/s to 30 m/s) or slow down (-20 m/s to -10 m/s). • tangent line: a straight line that touches a curve in only one point. • Sample Problem • At the start of a race, a toy car increases speed from 0 m/s to 5.0 m/s as the clock runs from 0 s to 2.0 s, Find the acceleration of the toy car.