Physics Error Reasons Physics questions are wrong and urgent

Only when the initial velocity is zero (vertical direction) can you use t=root number 2*6l g, and the title does not say that the initial velocity is zero.

Child, the rated power is 60kw, which does not mean that the car will do work at this power as soon as it starts.

The power of the engine is related to the speed of the engine, and the rated power refers to the power when the rated speed of the engine is reached. The engine speed is controlled by the throttle, and when the throttle is pressed to the end, the rated speed is reached.

For this problem, f is constant, v is constantly increasing, so the power of the engine p=fv is increasing. When the rated power is increased, it cannot be increased again.

Upstairs made the answer to this question, but the idea was completely wrong, but I didn't know enough about life to figure out the real meaning of p=fv here.

By the way, I'll give you an explanation.

f=f friction + ma = 5 * 1000 * 10 *, take g = 10m s 2p = 60kw

So the maximum velocity is v=p f=60*1000 10000=6m s, so the acceleration time is t=v a=6 1=6s

The question is not wrong, it just asks you how long the car can maintain such a motion, that is, how long can the car maintain a "uniform acceleration linear motion with an acceleration of 1m s", and the question is the time asked.

Your analysis is preceded by the correct.

Since p=fv

p is constant, and v is increasing due to uniform acceleration.

So f is constantly decreasing.

When f decreases to just equal to ma+f, the car cannot provide a larger f to maintain the original motion state as v increases. That is, how long the car has been moving when f=ma+f.

From this, v can be obtained, and t can be calculated according to the relationship between acceleration a and velocity v

The resistance is f= = 5000n

The power of the engine p= fv

When the traction force of the engine = drag, the speed reaches the maximum, the acceleration = 0p = fv = fv , v = 12m s

Your understanding is correct, a is a changing quantity, and the original intention of the question is to let you understand the formula p=fv.

How to calculate, you should make it clear.

The voltage of the sliding rheostat.

Total current = p=

You write down the process.

Normal light, the voltage at both ends of the bulb, the voltage at both ends of the sliding, series connection, current, rated p=.

I don't know, right?

19. Solar energy is one of the key energy sources for development and utilization in the 21st century. A solar-powered vehicle is a new type of motor vehicle that uses solar cells to convert the received solar energy into electrical energy and then uses an electric motor to drive it. （1）

There is a solar experimental vehicle (a sample of the development process), the effective area of the solar receiving panel on it is s=8m2, when the sun is clear and the receiving panel is facing the sun, the power of the sun can be received per square meter of area is p0=1kw, the voltage generated by the solar cell is u=120v, and the current that can supply the power motor is i = 10a. Seeking:

1) How efficient is the solar cell at converting solar energy into electricity when the motor is working normally?

2) If the motor is working normally. The efficiency of converting electrical energy into mechanical energy is 75%, and the traction force obtained when the car is driving in a straight line along the horizontal road surface at a constant speed is 150N, then what is the speed of the car when driving at a constant speed?

3) if the mass of the car itself is 90kg, and the resistance when driving along the horizontal road surface is 1 10 of the gravity of the car, then, how much cargo can the car load when driving at a constant speed along the horizontal road surface? (g=10n/kg)

4) Through the above introduction and related calculations, you have a general understanding of the relevant technical parameters and performance of the car. If you are one of the reviewers, do you think that the experimental car will be able to be mass-produced and put on the market? Name at least two reasons.

There should be a detailed explanation and a detailed calculation process (the more detailed the better, it is better not to skip steps).

1.A communication satellite located above the equator and stationary relative to the ground is called a geostationary satellite, what is the period t of a geostationary satellite? How high is the height h of the satellite from the ground? (It is known that the mass of the earth m=6*10 24kg, and the radius of the earth r=.)

The horizontal component and the vertical component of the supporting force of this inclined plane are equal, let the magnitude of the component be ma, then the acceleration of the object to the left is a, the downward acceleration is g-a, and the pressure of the inclined plane to the ground is mg+ma, so the acceleration to the right of the inclined plane is a-ug-ua The acceleration of the object relative to the inclined plane is forty-five degrees downward, so the vertical relative acceleration is equal to the horizontal relative acceleration, that is, a+(a-ug-ua)=g-a, and the solution is a=(1+u) (3-u)g

The inclined plane acceleration is a-ug-ua, so I have to give so many questions, I say that acceleration refers to the magnitude of acceleration, and I don't pick the direction carefully.

1. Because the definition of current is the direction in which a positive charge moves, and an electron is a negative charge, the direction of the current is opposite to the direction of the free electron.

2. This is determined by the chemical reaction inside the battery: the zinc in the dry battery you mentioned loses electrons in the reaction and becomes positively charged zinc ions, and the lost electrons flow back to the positive electrode (carbon rod) of the battery through the wires outside the battery. This creates a current outside the battery from the positive electrode (carbon rod) to the negative electrode (zinc cylinder).

Inside the battery, the current flows from the negative electrode to the positive electrode, and the current forms a loop inside and outside the battery.

Here, the electrostatic force is driving the electrons,Electrons have a negative charge！So billion is not wrong.

It is true that the electrostatic force pushes the positive electrode of the free electron towards the negative electrode.

The direction of directional movement of electrons is opposite to the direction of the current.

Positive charge at the positive electrode and negative charge at the negative electrode. Physics stipulates that the direction of movement of the positive charge is the direction of the current, and the actual positive charge does not move. The electrons in the electric current are the negative charges referred to.

That's right, but you misunderstood.

Then -2 is right.

L3 That's already an absolute displacement.

The total time of the shed state is t1 + t2 + t3 = 14s t2 + t3 = 12s".

In the above formula: through the platform's Shidan Tanjian 2s, you don't have a chain and the source is counted.

This,[Treadmill:L3=VT1+1 2A2T1 T1=2S] L3=[VT1+1 2A2T1] V0*T1 】Treadmill Wang Wu also moves. That distance l3 is an absolute bit of sleepiness or shift = quite + traction, but the traction is negative.

Blind and pure...

1. Metals can transfer electric charge, glass cannot.

2 is the size...

3. The directional movement in the circuit is generally electrons, and only in the solution does the directional movement of cations occur.

The resistance of 4 people is much smaller than that of the wire, so if the person is short-circuited, there will be no point.

Only C is right.

The mass of the x-nucleus is equal to the y-nucleus, and the mass of the z-nucleus is 3 smaller than the y-nucleus and 3 smaller than the x-nucleus

The x-nucleus has one more positive electroless late charge than the y-nucleus and two more positive charges than the z-nucleus. But the total charges are not known, and their multiples relationship cannot be determined.

c pair Let the mass number of the x nucleus be a and the number of charges be b

The mass of the y-nucleus is c, and the charge number is d

The mass number of the z-nucleus is m and the number of charges is n

Option A is patently wrong (not one more atom); Limb Sakura.

From the X nucleus, a positive electric first bub is released and then becomes a Y nucleus, which obtains A=C, B=1+D, and the Y nucleus reacts with protons to generate a Z nucleus and releases a helium (4,2He), which gives C=M+3, D=N+1

Use the number of neutrons, mass, and charge to know that option b is wrong (not one less neutron, but one more);

Option d is wrong (is 2 times).