So here's a problem we had in physics: Car weighs 1000 kg. How much force does it take to move from 0-30 mph? To 30-60 mph? For reference: Kinetic Energy= 1/2(mass)(velocity)^2 One of my classmates didn't understand why the amount of energy wasn't the same for both. He's pretty smart, gets A's. The answer is that the graph of the function of the velocity was a quadratic (a curve). Essentially, this means that the velocity is not proportional to the energy. He had a conniption, and just kept trying to justify that the amount of energy from 0-30 and 30-60 would be the same, and that the point of observation mattered. It was a little pathetic to be honest. Just thought I'd share.
No, my mimd can not comprimend this question I ask that there is a new rule. No posts can be longer than 8 words, or else i get confused. It is for my own good
I don't understand this student's argument, I'm a year 10 science teacher and have never had a student argue with the laws of physics. I'll run through the question for those that are unable to do it themselves at the beginning car has velocity 0, therefore according to the rule Ke=(1/2m)(v)^2 the kinetic energy is also 0 (I'm going to change the speeds to kilometres to simplify it for myself and velocity is usually measured in the most practical measurement so for me that is metres per second m/s) Once the car is going at 30km/h we can plug that into our equation Ke=(1/2 x 1000)(8.3)^2 Ke=(500)(69.4) Ke=34694.5 so the change in force from 0 km/h to 30km/h is 34694.45N (newtons the unit for the measurement of force) now to calculate the change in force from 30 to 60, since we already know the answer to the Ke of 30km/h we can just find out the Ke for 60km/h Ke=500(16.7)^2 ---> we can already see that we are going to have a different result don't we? Ke=500(278) Ke=139445 so the change from 30km/h to 60km/h can be found by subtracting 34694.45N from 139445N which gives a value of 104750.55N
He's actually quite smart, I'm just assuming 4 things happened: 1) Mind block on basic algebra constant: the function of the velocity is quadratic, not linear, meaning that the kinetic energy and the velocity of the object are obviously cannot be proportional. 2) This was first period, so... 3) Our teacher isn't the sharpest tool in the toolshed, to say the least, and he, as well as most of my class, really looks down at her intelligence, so he probably just assuming she was wrong as a principle (one of the very few things I don't like about him). 4) Because this is our first real physics class, many of the students have trouble understanding that these laws are absolute, and cannot just be changed with simple algebra or calc (for example, he likes to put his problems into Wolfram Alpha to solve, which has bitten him in the ass on several occasions).
