A physics textbook is launched up a rough incline with a kinetic energy of 200 joules. When the book comes momentarily to rest near the top of the incline, it has only gained 180 joules of gravitational potential energy. About how much kinetic energy will it have when it returns to the launch point?
KE -PE = 200 -180 = W(fr).
PE = W (fr) = 180 -20 = 160J
xixixixixixi i donnot know
To find out how much kinetic energy the physics textbook will have when it returns to the launch point, we can use the principle of conservation of mechanical energy.
The principle of conservation of mechanical energy states that the total mechanical energy of a system remains constant if no external forces, such as friction, are acting on it. In this case, we can assume that the only external force acting on the physics textbook is the friction on the rough incline.
We are given that the initial kinetic energy of the textbook is 200 joules and that it gains 180 joules of gravitational potential energy when it comes momentarily to rest near the top of the incline. Therefore, we can calculate the total mechanical energy at that point as the sum of the initial kinetic energy and the gained gravitational potential energy:
Total mechanical energy = Initial kinetic energy + Gained gravitational potential energy
Total mechanical energy = 200 J + 180 J
Total mechanical energy = 380 J
Since no external forces are acting except for friction, and we know that no work is done against friction during the upward journey (since the book slows down but does not come to a complete stop), we can conclude that the total mechanical energy will remain constant during the entire journey.
Therefore, the kinetic energy of the physics textbook when it returns to the launch point will be equal to the total mechanical energy at any point, which is equal to 380 joules.