Physics question: If a kid is crossin the road, and I hit him in a car at 45 mph..
- Thread starter platinumike
- Start date
ok well in the scenario lets say the kid is 5'4 and the car is a typical sedan that is like 4 ft 10 high or so.
SonnyDaze
Diamond Member
- Jul 31, 2004
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I'm not a kid but I was hit by a car at approx. 30 mph and I rolled up onto the windshield and then when the driver hit the brakes I rolled back across the hood and onto the pavement. I'm probably about 6' tall and the bumper hit me at just above mid calf (the front licencse plate screws left a nice hole in my calf). The car was a Cadillac IIRC.
MagnusTheBrewer
IN MEMORIAM
- Jun 19, 2004
- 24,122
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Even if he flips over the car, he will still move in the direction the car is travelling in relation to the point at which you hit him.
irishScott
Lifer
- Oct 10, 2006
- 21,562
- 3
- 0
Sedan/Coup: Probably hit the windshield and stay plastered there. If the car is extremely streamlined and low, he may go over the top.
SUV/Van/Pickup: Might hit the windshield, but will most likely go forward until you run him over.
Tractor Trailer: Forward until splat.
SUV/Van/Pickup: Might hit the windshield, but will most likely go forward until you run him over.
Tractor Trailer: Forward until splat.
Stupid question: If I take a ****** outside and the wind is blowing really hard, which direction will my ****** fly?
Kid's velocity is 0.
Car's velocity is 45.
Kid is not going to go instantly go from 0 to 45 in the split second after the hit. Therefore, the direction of kid is foward only as fast as his rate of acceleration. One can deduce that kid's velocity will not immediately match car's and kid will accelerate until matching car's speed or until car is no longer providing the force to accelerate kid.
In simpler terms, a kid would fly up on the hood get knocked under the car or be stuck to the grill not because that's the way the force is moving, but because the kid can't accelerate to 45mph at the instant s/he is hit. If the speed of the car continues and the kid is in a position to be constantly moved in the same direction, the kid will eventually get up to 45MPH and be moving with the car. If the brakes are applied, the mass of the car and friction of the brakes will cause it to slow faster while the lighter mass of the kid will make him/her take longer to slow down, thus kid goes foward further than the car. Pavement could drastically add friction to the kid and slow them down faster.
Whether the kid goes on the hood, under the car or eats the grill is determined by point of impact, as that could make the kid's head, legs, torso or any other part accelerate faster than the others. If a kid is struck in the legs, then the legs are going to start moving and the waist up are going to accelerate slower.
If order for him to go flying foword instead of being "carried" the car would probably have to come to a dead stop in the same second as the kid is hit.
Car's velocity is 45.
Kid is not going to go instantly go from 0 to 45 in the split second after the hit. Therefore, the direction of kid is foward only as fast as his rate of acceleration. One can deduce that kid's velocity will not immediately match car's and kid will accelerate until matching car's speed or until car is no longer providing the force to accelerate kid.
In simpler terms, a kid would fly up on the hood get knocked under the car or be stuck to the grill not because that's the way the force is moving, but because the kid can't accelerate to 45mph at the instant s/he is hit. If the speed of the car continues and the kid is in a position to be constantly moved in the same direction, the kid will eventually get up to 45MPH and be moving with the car. If the brakes are applied, the mass of the car and friction of the brakes will cause it to slow faster while the lighter mass of the kid will make him/her take longer to slow down, thus kid goes foward further than the car. Pavement could drastically add friction to the kid and slow them down faster.
Whether the kid goes on the hood, under the car or eats the grill is determined by point of impact, as that could make the kid's head, legs, torso or any other part accelerate faster than the others. If a kid is struck in the legs, then the legs are going to start moving and the waist up are going to accelerate slower.
If order for him to go flying foword instead of being "carried" the car would probably have to come to a dead stop in the same second as the kid is hit.
SunnyD
Belgian Waffler
Correct answer is one of two things:
A) Kid would head toward the hospital.
or more likely
B) Kid would head toward the nearest lawyer.
A) Kid would head toward the hospital.
or more likely
B) Kid would head toward the nearest lawyer.
But what if the kid was on a treadmill that was traveling at exactly the speed his feet were moving? Would the kid take off?
Only if his head is rotating at the exact opposite speed of his body while the speed of the treadmill is 1 with the speed of the kid being .999...
Jeff7
Lifer
- Jan 4, 2001
- 41,596
- 19
- 81
Depends upon a few things:
His center of gravity and where the impact occurs relative to this
His velocity
His mass
His moment of inertia
The amount of friction between his feet and the ground
It's safe to say that his net motion will be in the direction of the car's travel. However, his body above his center of mass may experience motion in the opposite direction, at least for a brief moment.
His center of gravity and where the impact occurs relative to this
His velocity
His mass
His moment of inertia
The amount of friction between his feet and the ground
It's safe to say that his net motion will be in the direction of the car's travel. However, his body above his center of mass may experience motion in the opposite direction, at least for a brief moment.
Demon-Xanth
Lifer
- Feb 15, 2000
- 20,551
- 2
- 81
My car he'll be in the grill. My dad's he'll be clobbered by the axles. My sister's he'll be rolling over the car.
...of course, it also depends on the kid. If the kid is Eric Cartman he'll eat the car.
...of course, it also depends on the kid. If the kid is Eric Cartman he'll eat the car.
he will be given horizontal velocity in the same direction you are travelling, and assuming he's not a midget he will be given vertical velocity as well. as he rolls up and over the car, he will continue to travel horizontally, in the same direciton you are. presuming you keep on driving and he rolls off the top and behind the car, he will have travelled a distance from the point of impact in the same direction you drove.
i suppose it is possible he could crash through the windshield if he was somewhat like a deer, but you can safely presume he will roll off the top in most situations.
i suppose it is possible he could crash through the windshield if he was somewhat like a deer, but you can safely presume he will roll off the top in most situations.
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