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F5 PHYSICS (MECHANICS)
我想問個Vmax 可以由 increase normal reaction 去increase 咁要increase normal reaction 點解一定要由increase fractional force 點解5可以increase mg (ie increase the mass of the car) 第2個問題係o係 letture notes 既p.32頁 Fnet mv^2 radial = r =>if friction (increase) =>then V (increase) or r(decrease) 咁可5可以同時V(increase) & r(decrease) ... 顯示更多 我想問個Vmax 可以由 increase normal reaction 去increase 咁要increase normal reaction 點解一定要由increase fractional force 點解5可以increase mg (ie increase the mass of the car) 第2個問題係o係 letture notes 既p.32頁 Fnet mv^2 radial = r =>if friction (increase) =>then V (increase) or r(decrease) 咁可5可以同時V(increase) & r(decrease) 我想問會5會有以上既情況出現OR 點解以上既情況不會出現thx for answering!!!!!! 更新: 咁如果: fractional force Ff has reached to its maximun, does it mean either V(increase) or r(decrease) will happen ??
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1. You have not given under what situation the car turns a corner. I could only provide my answer based on the most simple configuarion, i.e. a car turns a corner on a rough leve road. Suppose a car of mass m turning a corner of radius r at a speed v. The centripetal force required for turning is provided by friction on the road, then mv^2/r = Ff -------------------------- (1) where Ff is the frictional force For a given car and a given corner, the max speed for turning v(max) is found when the frictional force reaches its max value, i.e. when Ff = uR, where u is the coefficient of friction and R is the normal reaction. Hence, m[v(max)]^2/r = uR but R = mg on a level roas, we have, m[v(max)]^2/r = u(mg) v(max) = square-root[r.u.g] -------------------- (2) The above equation shows that v(max) is actually independent from the mass of the car. --------------------------------------------------------- 2. I don't know what lecture notes you refer to. From equation (1) above, as far as the frictional force Ff has not yet reached its max value, you could increase both v and r simultaneously.
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F5 PHYSICS (MECHANICS)
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發問:我想問個Vmax 可以由 increase normal reaction 去increase 咁要increase normal reaction 點解一定要由increase fractional force 點解5可以increase mg (ie increase the mass of the car) 第2個問題係o係 letture notes 既p.32頁 Fnet mv^2 radial = r =>if friction (increase) =>then V (increase) or r(decrease) 咁可5可以同時V(increase) & r(decrease) ... 顯示更多 我想問個Vmax 可以由 increase normal reaction 去increase 咁要increase normal reaction 點解一定要由increase fractional force 點解5可以increase mg (ie increase the mass of the car) 第2個問題係o係 letture notes 既p.32頁 Fnet mv^2 radial = r =>if friction (increase) =>then V (increase) or r(decrease) 咁可5可以同時V(increase) & r(decrease) 我想問會5會有以上既情況出現OR 點解以上既情況不會出現thx for answering!!!!!! 更新: 咁如果: fractional force Ff has reached to its maximun, does it mean either V(increase) or r(decrease) will happen ??
最佳解答:
1. You have not given under what situation the car turns a corner. I could only provide my answer based on the most simple configuarion, i.e. a car turns a corner on a rough leve road. Suppose a car of mass m turning a corner of radius r at a speed v. The centripetal force required for turning is provided by friction on the road, then mv^2/r = Ff -------------------------- (1) where Ff is the frictional force For a given car and a given corner, the max speed for turning v(max) is found when the frictional force reaches its max value, i.e. when Ff = uR, where u is the coefficient of friction and R is the normal reaction. Hence, m[v(max)]^2/r = uR but R = mg on a level roas, we have, m[v(max)]^2/r = u(mg) v(max) = square-root[r.u.g] -------------------- (2) The above equation shows that v(max) is actually independent from the mass of the car. --------------------------------------------------------- 2. I don't know what lecture notes you refer to. From equation (1) above, as far as the frictional force Ff has not yet reached its max value, you could increase both v and r simultaneously.
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