Ok this question is based upon a real life experience. I am in a vehicle on a relatively straight road that goes on for miles. My vehicle is traveling at a relative speed of 85 mph. I notice a vehicle in my rear-view mirror just enter the extreme range of that mirror's vision. I aproximately 5 seconds I was passed by this vehicle and was in the extreme range of my forward vision. The day was sunny and clear with no glare from the sun. How fast was this vehicle going relative to my observation point as driver of the vehicle going 85?
This car was moving so fast that I could not possitively identify and of it features every thing was a blur. I think that it was greyish. You can assume any relative distance between my vehicle and the two extreme ranges. I have perfect 20/20 vision if that helps. I just seem to be drawing a blank on how to approach this problem. It's not urgent just bugs me.
2006-11-24 05:14:57 · 4 answers · asked by ikeman32 6 in Science & Mathematics ➔ Mathematics
The 5 seconds is an aproximate estimate the total time was definately less than 10 seconds
2006-11-24 05:51:30 · update #1
Let's assume your range of vision was 0.2 miles infront of you, and 0.1 miles behind with the mirror. (I'm pulling these numbers out of my behind.)
At t=0, the car was at position x = -0.1 relative to you.
At t=5 seconds, it was at x = 0.2.
So the speed (relative to you) is 0.3 miles / 5 seconds = 0.06 miles per second = 216 miles per hour. Since you were doing 85 mph, it real speed was 301 mph.
Are you sure this took only 5 seconds? I picked some pretty small numbers for the range of vision and this still results in some wicked speed.
2006-11-24 05:41:32 · answer #1 · answered by Anonymous · 1⤊ 0⤋
When people say that motion is relative, they mean what you described - you can be moving 40 mph north relative to the ground, 10 mph south relative to me, and not moving at all relative to your car. As long as you make all your measurements are made from the same perspective, they are consistent with the laws of physics, for example, a force causes acceleration according to F = ma. No perspective is more correct. "Speed" means something particular, so you can't just use your own definition. Speed is the magnitude of velocity. For example, 10 m/s towards the north is a velocity, and 10 m/s is a speed.
2016-05-22 22:33:45 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The eye can process 16 distinct events in one second after which it is a blur.
Assuming length to be 2 metres, this car was going at more than 32 m/s relative to you that means 115.2 km/hr relative to you.
2006-11-24 05:22:33 · answer #3 · answered by ag_iitkgp 7 · 0⤊ 0⤋
The matter is that a driver like any human is very poor in evaluation of time. It depends on your health condition, age, activity etc. You were in a monotonous state, weren’t you? You had no stop watch, had you? So your estimation for 5s could be 15s in reality. Biologists could explain it
in better terms and more persuasive.
2006-11-24 08:13:56 · answer #4 · answered by Anonymous · 0⤊ 1⤋