Mike2015 Posted October 28, 2015 Share Posted October 28, 2015 Can anyone help please I drive a car that weighs 1000kg, I hit the car in front that weighs 3000 kg. How far would the car in front move if I hit it at 30 mph, 40mph and 50mph. Thank you Link to comment Share on other sites More sharing options...
mathematic Posted October 29, 2015 Share Posted October 29, 2015 You need to specify how much damage these cars suffer. More damage results in less motion. Link to comment Share on other sites More sharing options...
Function Posted October 29, 2015 Share Posted October 29, 2015 mph? Heathen! Don't work with that terrible unit 1 Link to comment Share on other sites More sharing options...
Greg H. Posted October 29, 2015 Share Posted October 29, 2015 It depends on whether the collisions are elastic or inelastic - in other words, are you making the assumption that the cars crumple and deform as they really would in a collision or does 100% of the kinetic energy go to moving the target vehicle. One case is relatively simple. The other is not. 1 Link to comment Share on other sites More sharing options...
swansont Posted October 29, 2015 Share Posted October 29, 2015 The two cases most easily solved are perfectly elastic (no damage) and perfectly inelastic (cars stuck together). Then there's the spectrum of inelastic collisions in between. 3 Link to comment Share on other sites More sharing options...
Acme Posted October 29, 2015 Share Posted October 29, 2015 Also of consideration is what gear -if any- the struck car is in, whether its parking brake is set, and the slope of the pavement. Link to comment Share on other sites More sharing options...
ydoaPs Posted November 12, 2015 Share Posted November 12, 2015 The two cases most easily solved are perfectly elastic (no damage) and perfectly inelastic (cars stuck together). Then there's the spectrum of inelastic collisions in between. The "how far" can't be answered with the information given. We need to know the effective coefficient of friction as well. If we're not assuming friction, then the answer is "infinitely far". Link to comment Share on other sites More sharing options...
Sensei Posted November 12, 2015 Share Posted November 12, 2015 (edited) If we're not assuming friction, then the answer is "infinitely far". That would require not existence of gravitational force of Earth, Moon, Sun and Galaxy. Velocities acquired during hit of two cars, are far less than escape velocities of either cosmic objects mentioned above. Edited November 12, 2015 by Sensei Link to comment Share on other sites More sharing options...
ydoaPs Posted November 12, 2015 Share Posted November 12, 2015 That would require not existence of gravitational force of Earth, Moon, Sun and Galaxy. Velocities acquired during hit of two cars, are far less than escape velocities of ether cosmic object mentioned above. You're ruling out the possibility that it just loops the Earth. If there's no friction, there's no reason why it wouldn't (unless it ramps up a hill too much taller than the kinetic energy allows, of course). Link to comment Share on other sites More sharing options...
Sensei Posted November 12, 2015 Share Posted November 12, 2015 You're ruling out the possibility that it just loops the Earth. If there's no friction, there's no reason why it wouldn't (unless it ramps up a hill too much taller than the kinetic energy allows, of course). You're ruling out time. Cosmic trash (remains from rockets and satellites) won't stay on orbit infinite long. They will either escape or the most likely fall back to the Earth. It's just a matter of years, thousands years or million years. Energy are all the time absorbed by them from the Sun, and stars, and emitted by radiation of hot black body. Everything on orbit is just for a while (perhaps billions years "while") (meta)stable orbit. Link to comment Share on other sites More sharing options...
swansont Posted November 12, 2015 Share Posted November 12, 2015 You're ruling out time. Cosmic trash (remains from rockets and satellites) won't stay on orbit infinite long. They will either escape or the most likely fall back to the Earth. It's just a matter of years, thousands years or million years. Energy are all the time absorbed by them from the Sun, and stars, and emitted by radiation of hot black body. Everything on orbit is just for a while (perhaps billions years "while") (meta)stable orbit. I think you're missing the practice of not introducing too many complicating details into physics problems. Link to comment Share on other sites More sharing options...
Sensei Posted November 12, 2015 Share Posted November 12, 2015 I think you're missing the practice of not introducing too many complicating details into physics problems. ? Sorry, but I didn't ask for "coefficient of friction" in the first place... Link to comment Share on other sites More sharing options...
swansont Posted November 12, 2015 Share Posted November 12, 2015 ?Sorry, but I didn't ask for "coefficient of friction" in the first place... No, that's not it. You're introducing cosmic debris, which is way beyond the scope of the question. Link to comment Share on other sites More sharing options...
ydoaPs Posted November 12, 2015 Share Posted November 12, 2015 ? Sorry, but I didn't ask for "coefficient of friction" in the first place... An effective coefficient of friction isn't a complicating detail. It's a necessary piece of information to be able to answer the question. Link to comment Share on other sites More sharing options...
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