sawq さんの書込 (2008/10/18(Sat) 08:40)

お手数ですがよろしくお願いします The coefficients of the friction between the tyres of a car and the road are μ0 = 0:6 and μ = 0:5. (a) If the resultant force on the car is the force of static friction exerted by the road, what is the maximum acceleration of the car? [μ0g = 5:886m/s2] (b) What is the least distance in which the car can stop if it is initially travelling at 30 m/s and the wheels do not slip? [76.45 m] (c) What is the stopping distance if the wheels skid so that the stopping 4.11. A car accelerates along a flat road. If the car is to accelerate from 0 to 99 km/h in 12 s at constant acceleration, what is the minimum coefficient of friction needed between the road and the tyres? (Assume the wheels do not spin.) [0.23] 4.12. A chair is sliding across a polished floor with an initial velocity of 3 m/s. It comes to rest after sliding 2 m. What is the coefficient of kinetic friction between the floor and the chair? [0.23] 4.13. A spring has a force constant k = 200 N/m. A 5-kg object is suspended from the spring. Find (a) the numerical values of all forces acting on the object and [weight = spring force = 49.05 N] (b) the extension of the spring from its equilibrium position. [0.24525 m]

ミュフ猫 さんのレス (2008/10/18(Sat) 10:26)

ここまで居直った丸投げは，かえって痛快ですね・・・．

yokkun831 さんのレス (2008/10/18(Sat) 14:25)

こんにちは．

1. If the force on the car is the maximum force of static friction, what is the dynamical equation of the car ? The maximum acceleration of the car will be found from it.
2. If the force on the car is the maximum force of static friction, the car can stop in the least distance.

(c) I think it's the same as (b), but you must use the force of kinetic friction. 4.11 and 4.12 can be solved if you understand from (a) to (c). You must use the next relations.

or

4.13 Weight( ) and spring force( ) are balanced each other if the object is at rest.

sawq さんのレス (2008/10/18(Sat) 21:12)

ありがとうございます