IneedA said:
(60km/h)(1h/3600s)(1000m/1km)=16.667 m/s
5sx16.667 m/s=83.335 m
100m>83.335m
. Well, I live next to ucla, usc, and caltech. These schools don't like B’s. The pressure is intense. I get stressed when I see a 90% as opposed to 100%.
I got a B on a midterm. I was stressed seeing my grade at 91% the rest of the semester.
Physics is not until fall so i have time to learn. I have calculus 1 in summer.
I know physics will be my most difficult course. Some people at my college are just going to take physics with easier professors at another college. I am not about it. I want to take physics as it was intended. I just need to know exactly what steps I should to give me the best chance for an A.
I see a lot of numbers but no answer. Will the driver be able to get out in time and why? You need to supply
words explaining what the numbers mean.
It looks like you used a calculator to answer this question. Here is how you can do it in your head.
- The train moves at 60 km/h. Since 1 hour has 60 minutes, the train travels one kilometer every minute.
- One kilometer has ten one-hundred-meter intervals.
- One minute has ten six-second intervals.
- Therefore the train will cover the one hundred initial distance in six seconds.
- Thus, the driver can get out with one second to spare.
As far as problem-solving in physics is concerned, I would advise you to use the SIMA step-by-step method,
Strategy,
Implementation,
Manipulation,
Answer which I used in my classes.
Strategy (Must contain words and only words; no symbols no equations, no numbers)
Here you explain the logical path that you will follow to answer the question.
Implementation (Must contain words and equations but no numbers)
Here you model the physical situation and use equations to describe mathematically what you said you will do in the previous step. The words that you use must justify the use of the equations, e.g. why this particular equation and not some other equation.
Manipulation (Must contain mostly equations and some words but no numbers)
Here you manipulate the equations algebraically, to get an algebraic expression where the quantity you are asked to find is on the left side and a whole bunch of symbols on the right side.
Answer (May contain numbers if a numerical answer is required)
Here you state the answer to the problem so that the person who evaluates your solution will not have to dig into your scribblings to find it.
So let's illustrate the use of the SIMA method to the stranded car problem.
Strategy
I will calculate the time it takes for the train to travel the initial distance to the stranded car. If this time is more than five seconds, the driver will safely make his escape.
Implementation
We know that the displacement ##\Delta x## of the train moving at constant speed ##v## as a function of time ##t## is given by the equation $$\Delta x=Vt.$$
Manipulation
Solving this equation for the time gives $$t=\frac{\Delta x}{V}.$$ When I replace the initial distance and train speed in this expression, I will get the collision time.
Answer
$$V=60~\left(\dfrac{\text{km}}{\text{h}}\right)\times 1000~ \left(\dfrac{\text{m}}{\text{km}}\right)\times \dfrac{1}{3600} \left(\dfrac{\text{h}}{\text{s}}\right)=\dfrac{100}{6}~\left(\dfrac{\text{m}}{\text{s}}\right). $$ $$t=\frac{\Delta x}{V}=\frac{100~\text{m}}{\dfrac{100}{6}~\left(\dfrac{\text{m}}{\text{s}}\right)}=6 ~\text{s}.$$ Since the train reaches the car in 6 s, the man can escape with one second to spare.
Presenting clearly what you plan to do, explaining what you are doing as you go along, using symbols so that your algebraic manipulations are transparent will get you better grade than just throwing numbers around. Instructors are not mind readers. It is your job to demonstrate to them the extent of your knowledge and understanding.
"Well", you might ask, "who has the time during a physics exam to lay out the solution using the SIMA method?" The student who needs an A, that's who.
The SIMA method is not new. If you think about it, several professions rely on it to solve problems. A doctor will listen to your health problem and suggest a strategy to address it, e.g. we have to do a bunch of tests. At the implementation stage blood is drawn and x-rays taken. At the manipulation stage the doctor assembles the collected evidence to come up with the cause of your health problem. At the answer stage, you are given a supply of pills to take once a day.
Police detectives work the same way. When they find a dead body say, they first develop a strategy, canvas the neighborhood, look for surveillance camera footage etc. Then they implement the strategy by doing just that, then they digest the information to see if it points to a suspect and in the end they find whodunnit.