physics, math, astronomy,... questions

[epicstruggle]

Ok ive had a couple of question in the back of my head. Ill ask them one at a time. If other have questions please feel free to add to this thread.

q1. is it possible for a car to climb a ramp of a moving truck, the ones that carry cars, (something like this) and stop when the back tires are just barely on the ramp. Does it matter if the car has rear/front/all/4wd wheel drive?

 

[Xmas]

Yes that is possible, no matter what drive. Imagine the car is just rolling faster than the truck, without any acceleration. When the front tires touch the ramp they have a turning momentum, but no force to keep it up. If the tires are revolving too fast they'll just don't get a grip on the ramp. If they are revolving slowly, their momentum is hardly enough to accelerate the car notably relative to the truck in an instant. Same goes for the rear tires. If the driver brakes in the right moment, stopping just barely after the rear tires touch the ramp should be entirely possible.

 

[ByteMe]

I would think it would be cooler if the car driver just floored it and used the ramp to jump over the truck.

 

[epicstruggle]

Yes that is possible, no matter what drive. Imagine the car is just rolling faster than the truck, without any acceleration. When the front tires touch the ramp they have a turning momentum, but no force to keep it up. If the tires are revolving too fast they'll just don't get a grip on the ramp. If they are revolving slowly, their momentum is hardly enough to accelerate the car notably relative to the truck in an instant. Same goes for the rear tires. If the driver brakes in the right moment, stopping just barely after the rear tires touch the ramp should be entirely possible.

I thought it might be something like this. but say i have a rear wheel drive. when the front tires get on thats fine. Half the car is on the ramp and as you are moving a little bit faster than the truck, you slowly move up the ramp. BUT when your rear wheels hit the ramp, and your going some relative speed (60mph) woulndt you then speed right up the ramp extremely fast?

later,
epic

 

[AAlcHemY]

But using a 4WD car would be very difficult imo. Imagine the front weels rotate very slow, and the ones on the rear mutch faster.
And epicstruggle,

If they are revolving slowly, their momentum is hardly enough to accelerate the car notably relative to the truck in an instant.

It doesnt have the time to accelerate ( compared to the truck ), like Xmas already said.

Edit: The only thing is, that you better be in a low gear, the engine can then simply go lower in rpm's.

 

[epicstruggle]

i understand what your saying, but if the car is traveling 60 miles/hour, as soon as the back wheels are on the ramp, arent the wheel still spinning at 60mph? Wouldnt that cause the car to go up the ramp extremely fast?

later,
epic

 

[Kyyla]

The angular momentum of the wheels won't affect the car much since the wheels are so light in comparison to the whole vehicle.

 

[Snyder]

I could see problems with automatic transmission. With manual transmission, you just have to hit the clutch early enough to break the power transmission from the engine to the wheels so the abrupt change of the wheel speed shouldn't be problematic.

 

[Simon F]

But using a 4WD car would be very difficult imo.

If you had a normal differential separating the drives to the front and rear axels it would probably be OK. (Note that I'm assuming most FWDs would either use a limited slip diff' or none at all).

 

[Simon F]

i understand what your saying, but if the car is traveling 60 miles/hour, as soon as the back wheels are on the ramp, arent the wheel still spinning at 60mph? Wouldnt that cause the car to go up the ramp extremely fast?

later,
epic

Only if you'd inflated your wheels with lead.

I imagine the tyres would have to be replaced fairly frequently if you did this stunt too often. I think the first time I saw this trick was in "The Italian Job". (That's "The 'you're only supposed to blow the bloody doors off' Italian Job", BTW).

 

[epicstruggle]

ok i think i see where my thinking is wrong. next question.

q2. is there a difference between the following numbers .000...001, .000...002, ..., .000...009? Arent they all equal to 0? So arent they the same number?

later,
epic

 

[Humus]

That depends on if "..." is a finite number of zeros or not.

 

[epicstruggle]

That depends on if "..." is a finite number of zeros or not.

... == infinite 0's
not easy drawing a line ontop of the zero.
later
epic

 

[chavvdarrr]

imagine that you're multiplying these numbers with something like:
100.......00000

 

[Simon F]

ok i think i see where my thinking is wrong. next question.

q2. is there a difference between the following numbers .000...001, .000...002, ..., .000...009? Arent they all equal to 0? So arent they the same number?

Your question is poorly defined.

What you want to ask is...

Does "lim (n->infinity) A/10^n = lim (m->infinity) B/10^m" where A and B belong to [0..9]?

The answer is yes.

 

[epicstruggle]

I agree that both values aproach 0, but does that mean that they =0 as n aproaches infinity?

q3. what is the current theory if 2 black holes collided?
q4. if 2 blackholes had barely overlapping event horizons, and i placed a beam of light that would run between the 2 bh, what would happen to the light beam? () | () where ()=black hole, and | is the beam of light.
q5. if i shot a beam of light towards a black hole, does light accelarate to a speed beyond the speed of light. What about using the sling shot effect to make light go faster than the speed of light?

later,
epic

 

[Neeyik]

q3. Depends on the massess of the black holes - they can end up in orbit around each other; a large one could "swallow" up a smaller one - just like with any large stellar mass.

q4. if the masses were equal and the light ray was equidistant from the two event horizons, it's fairly obvious what will happen.

q5. no it does not accelerate; however, it does change frequency.

 

[epicstruggle]

q4. if the masses were equal and the light ray was equidistant from the two event horizons, it's fairly obvious what will happen.

sorry, im a bit dense. , but exactly what would happen. I was thinking that something like this would happen:
A hole through the center of a planet. Drop a ball into said hole, and the ball would go almost all the way to the other end of the hole and fall back, back slowing loosing "height" until it settles in the center of the planet.

Is this what would happen? Except light would go back and forth?

later,
epic

 

[Neeyik]

It wouldn't roll back and forth - the ball in your example is only doing that because (a) it's kinetic energy is less than the increase in GPE required to "escape" the hole and (b) it's constantly losing KE thanks to friction. In the case of light, if the observer viewed the beam of light ahead of its journey between the black hole, he or she would see the light undergo blue shift as it approached the holes and then red shift as it moved away. If the event horizons were sufficiently tight enough, the light could undergo so much red shift that it would no longer be visible - but it wouldn't "roll back and forth", slow down or speed up.

 

[Simon F]

I agree that both values aproach 0, but does that mean that they =0 as n aproaches infinity?

AFAICS you can't actually say "here is the number 0.0<infinitely many 0s>A" but you can define what the limit of "0.0 <0 repeated N times> A" is because it is defined using finite expressions.

I think you just have to be careful with your wording so you can say that as n approaches infinity, the limit of the values is 0.