According to the law of conservation of mechanical energy The content of the law of conservation of mechanical energy says that only gravity (or spring force) does work. Does that mean that only spring force does work, and other forces can't?

According to the law of conservation of mechanical energy The content of the law of conservation of mechanical energy says that only gravity (or spring force) does work. Does that mean that only spring force does work, and other forces can't?

No, mechanical energy is always conserved. This is a special form of energy conservation. Energy is always conserved in the whole process of motion

Conservation law of physical mechanical energy in grade one of senior high school
If there is no mechanical energy loss when the ball collides with the ground and the air resistance is ignored, then the bounce height of the ball is zero
I exclude a, B and leave C. H - (VO ^ 2 / 2G) d. VO ^ 2 / 2G
I choose D, but I don't understand. Please explain

Obviously, the mechanical energy of the whole process is conserved, that is, the velocity of the ball when it returns to the throw position is still V0, but the velocity at this time is vertical, which is equivalent to throwing V0 upward at h. then the final height is H + (VO ^ 2 / 2G)
The difficulty is to see the conservation of mechanical energy in this process

A topic about "verifying the law of conservation of mechanical energy",
When doing the experiment of "verifying the law of conservation of mechanical energy", the following statement is correct
A. When selecting the heavy hammer, the heavy one with the same volume is better than the light one
B. When selecting the heavy hammer, the small one with the same mass is better than the large one
C. The weight should be weighed after selecting the heavy hammer
D. None of the above is true
Choose ABC

ABC is right,
On the one hand, in order to reduce the influence of air resistance, the weight should be as small as possible, that is, choose the material with high density
On the other hand, the choice of small weight can achieve frontal impact and improve the experimental accuracy
Three aspects of weighing, if you need quantitative experimental analysis, then you must weigh