BrokenBiker
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- Messages
- 11,271
- Location
- Newport, South Wales
my younger brother is doing a bit of physics in college and came to me with a question based upon Newton's laws and a few other things
first he wanted me to explain the laws to make sure he knew what they were, so I did in basic terms. first law, something will either be at rest, or in motion whilst maintaining a constant velocity, unless acted upon by another force. second law - F=ma. third law - equal and opposite reactions. simple.
so then he asked about transfer of energy. so I explained that due to conservation of energy, energy cannot be created nor destroyed, but merely converted to another form.
he looked like he nearly got it, but needed a bit more so I used a wheel and disc brake as an example (mainly because its the example I was given in college). when a wheel is moving at a constant velocity it has kinetic energy stored in it. when the pads close on the brake disc, the friction between the two convert the kinetic energy into heat energy, which is dissipated into the air around the disc (eventually). took him a few seconds but he got it. I did a brief bit on efficiency of discs cooling and he was happy he understood it
then we moved onto inertia, and this is where the problem started, as apparently his teacher hadn't bothered to discuss inertia at all. I explained that inertia is just the opposition to a change in either speed or direction. so when you corner in a car, it leans away from the corner, and when you apply a braking force to a wheel, it tries to keep on going, so if you want to stop quicker, you need a bigger stopping force, which means more friction to convert more of the kinetic energy into heat, quicker.
this apparently confused the trousers off him, as he couldn't understand what was keeping the wheel trying to move forward, while the brake was trying to stop it. his reasoning is, if the kinetic energy is being turned into heat energy and slowing the wheel, what energy is trying to keep it going. no matter what I said, I couldn't get through to him that inertia is a force, not energy. I even went as far as to compare it to gravity (in as much as gravity is a force and not an energy, to try and show the difference between force and energy), but no, he just cannot get his head around inertia, so in the end I suggested he ask his teacher why you get thrown forwards in a car if the brakes are slammed on.
I don't know how to explain it any differently to the way I understand it (because im not a teacher) and every example I use just goes over his head. its a shame I cant explain it better to him, he is far better at theory than I am most of the time, but cant do anything physical or use tools to do anything. he doesn't like getting dirty, baffles me
first he wanted me to explain the laws to make sure he knew what they were, so I did in basic terms. first law, something will either be at rest, or in motion whilst maintaining a constant velocity, unless acted upon by another force. second law - F=ma. third law - equal and opposite reactions. simple.
so then he asked about transfer of energy. so I explained that due to conservation of energy, energy cannot be created nor destroyed, but merely converted to another form.
he looked like he nearly got it, but needed a bit more so I used a wheel and disc brake as an example (mainly because its the example I was given in college). when a wheel is moving at a constant velocity it has kinetic energy stored in it. when the pads close on the brake disc, the friction between the two convert the kinetic energy into heat energy, which is dissipated into the air around the disc (eventually). took him a few seconds but he got it. I did a brief bit on efficiency of discs cooling and he was happy he understood it
then we moved onto inertia, and this is where the problem started, as apparently his teacher hadn't bothered to discuss inertia at all. I explained that inertia is just the opposition to a change in either speed or direction. so when you corner in a car, it leans away from the corner, and when you apply a braking force to a wheel, it tries to keep on going, so if you want to stop quicker, you need a bigger stopping force, which means more friction to convert more of the kinetic energy into heat, quicker.
this apparently confused the trousers off him, as he couldn't understand what was keeping the wheel trying to move forward, while the brake was trying to stop it. his reasoning is, if the kinetic energy is being turned into heat energy and slowing the wheel, what energy is trying to keep it going. no matter what I said, I couldn't get through to him that inertia is a force, not energy. I even went as far as to compare it to gravity (in as much as gravity is a force and not an energy, to try and show the difference between force and energy), but no, he just cannot get his head around inertia, so in the end I suggested he ask his teacher why you get thrown forwards in a car if the brakes are slammed on.
I don't know how to explain it any differently to the way I understand it (because im not a teacher) and every example I use just goes over his head. its a shame I cant explain it better to him, he is far better at theory than I am most of the time, but cant do anything physical or use tools to do anything. he doesn't like getting dirty, baffles me
