Tham khảo tài liệu 'sat ii physics (sn) episode 1 part 5', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Because the acceleration is negative which as we defined it is down for mass M and uphill for mass m. 2. WHAT IS THE VELOCITY OF MASS M AFTER MASS M HAS FALLEN A DISTANCE H Once again the in-clined plane is frictionless so we are dealing with a closed system and we can apply the law of conservation of mechanical energy. Since the masses are initially at rest . Since mass M falls a distance h its potential energy changes by Mgh. If mass M falls a distance h then mass m must slide the same distance up the slope of the inclined plane or a vertical distance of . Therefore mass m s potential energy increases by . Because the sum of potential energy and kinetic energy cannot change we know that the kinetic energy of the two masses increases precisely to the extent that their potential energy decreases. We have all we need to scribble out some equations and solve for v Finally note that the velocity of mass m is in the uphill direction. As with the complex equations we encountered with pulley systems above you needn t trouble yourself with memorizing a formula like this. If you understand the principles at work in this problem and would feel somewhat comfortable deriving this formula you know more than SAT II Physics will likely ask of you. Inclined Planes With Friction There are two significant differences between frictionless inclined plane problems and inclined plane problems where friction is a factor 1. There s an extra force to deal with. The force of friction will oppose the downhill component of the gravitational force. 2. We can no longer rely on the law of conservation of mechanical energy. Because energy is being lost through the friction between the mass and the inclined plane we are no longer dealing with a closed system. Mechanical energy is not conserved. Consider the 10 kg box we encountered in our example of a frictionless inclined plane. This time though the inclined plane has a coefficient of kinetic friction of . How will this additional 101 factor .
