Super difficult physics questions, who made it with his surname

d is incorrect. When the spring is thrown on the ground, there is only kinetic energy and elastic potential energy, and when it rises to the highest point, the kinetic energy becomes zero, at this time the kinetic energy is all converted into gravitational potential energy, while the elastic potential energy of the spring remains unchanged. So a is correct.

When rising to half the height, the gravitational potential energy at this time is half of the gravitational potential energy at the highest point, that is, 3 times the elastic potential energy, because the gravitational potential energy at this time is 4 joules greater than the elastic potential energy, so it can be calculated that the elastic potential energy is 2 joules, and the gravitational potential energy at this time is 6 joules. So BC is also correct.

The total mechanical energy is 12 2 14 joules. So d is incorrect.

Because the air resistance is not counted, the energy must be conserved, when it is just thrown, the gravitational potential energy is zero, the kinetic energy is the same as when it falls to the ground, and the elastic potential energy remains unchanged because the spring is tied by the rope. And at the highest point, the gravitational potential energy is the largest, and the kinetic energy is zero, so the gravitational potential energy is 12j, at this time, the gravitational potential energy is 6 times the elastic potential energy, so the elastic potential energy is 2j. When rising to half the height, the kinetic energy is the same as the gravitational potential energy, so it is 6j, while the total mechanical energy is the sum of kinetic energy, potential energy, and elastic potential energy, so it is 14j

So d is not right.

The spring is tied with a wire after compression, and the elastic potential energy does not change.

Regardless of air resistance, the whole process of ascent and descent is actually the conversion of gravitational potential energy and kinetic energy.

The gravitational potential energy is 12 joules at the highest point, 6 joules at the descent to half the height, and the elastic potential energy is 2 joules.

So, a, b, c are all true, d is false, total mechanical energy gravitational potential energy elastic potential energy kinetic energy 14 joules.

ps It's very simple, and it's super difficult physics?

；Solution: At the highest point there is: ep=6e; In the middle there is:

ep'-e=4j;On the ground: ek=12j; In the whole process, only gravity does the work, and the mechanical energy is conserved, so ep=ek=12j; So e=2j; So ep'=6j;So at half the time the kinetic energy is 6j; And the total mechanical energy of the object should be the sum of the potential energy and kinetic energy, i.e., e+ek=14j

D false. The mechanical energy is conserved, and when it falls to the ground, the kinetic energy is 12j, and it can be seen from the first half of the question that the elastic potential energy is 2j, and the total mechanical energy is 14j

You don't have to change your surname, just give more points,..

Solution: S hole = 20cm, S bottom = 200cm, H1 = 10cm = area of the top of the container: S = S bottom - S hole = 200-20 = 180cm = according to P= GH1, P =

According to p=fs, f=ps=1000

A: The pressure of water on the top of the container is 18N.

Note: g = 10 n kg

As you can see from the diagram, the pressure at the top of the container p p0 p1 , where p0 is the atmospheric pressure and p1 is the pressure generated by the water column at h1.

i.e. p p0 water * g * h1 pa.

The area of the top of the container is S top S bottom S hole (200 40)*10 (-4) square meters.

The pressure sought is fp*s top bull.

1. The work done to overcome its own gravity is 50*10*24=12000J, and the power = 12000 120=100W(Units are not included in the calculation).

2. The density of blood is about the same as that of water, and the work that the heart needs to do = 12000J 40% = 30000J

3. The heart can deliver 70cm3 of blood every 1 contraction, and the muscles do the work. The heart contracts (i.e., heart rate) 30000j 2 times per minute.

The v in the answer refers to the v corresponding to the fall height of h, not the v in time t, right?

0-mv is the final momentum minus the initial momentum, and this question is a test of the momentum theorem, and you will ask this kind of question, and it seems that you don't know this content at all.

v gt, yes, note that t should be the free fall time, not the t in the title. The free fall time is not directly given in the question, and it is better to get v according to h step.

The first question: what he asks for is the speed of the rope before it has a force on the person. And the t given in the question is the time spent by the person in the whole process of movement, so it is not possible.

The second question: The change in momentum is the initial momentum subtracted from the final momentum. The final momentum is zero, and the initial momentum is mv.

Figure 1: 1The lower left and upper right switches, (I can't see clearly, it should be s1.) s3）2.strong, semiconductor, superconducting.

2) w uit 120 10 600 720000 joules figure two: 1The bulb does not light up when it is short-circuited, select C

2.Plastic, 0, length.

1、d。I can't see the foot code of S in the figure, which should be as shown in Figure 2 below, strong, semiconductor, superconductive.

3、①p=1000x8=8000w

w=uit=120x10x10x60

720000j。

1, C2, plastic, 0, length.