Good or bad physics, solving, finding physical problems, easy to make mistakes

If you were to go to outer space, how much would you weigh?

Weight refers to the quality of the quality of the unchanged Pick 3 the same.

An object weighs 30 N, what is the mass of the object?

g=mg m=g g=30 10=3 kg Choose 2 a car brake and let it stop.

In a simple and easy-to-understand way, the friction of movement is experienced in the process of moving, and the friction of movement is experienced in the process of static friction at rest, and it must still be in motion in the process of stopping, so choose 1 moving friction.

The first question, I think, is that the question is whether the mass has changed, and if it is the mass, it is the same, and the weight generally does not occur in physics.

Question 2 If an object weighs 30 N, then the mass of the object is 3kg

Question 3 When the braking force of the car is emergency braking, the braking force on the ground against the tire is not static friction.

Because the general car is equipped with ABS brake anti-lock device. The working principle of ABS is: when braking, with the increase of pedal force, the braking force also increases rapidly, when it reaches a certain value, the tire gradually changes from rolling to sliding, at this time ABS detects that the car tire begins to slide, the system will reduce the braking force, so that the tire to the state of sliding friction, when returning to the state of rolling friction, the braking force begins to increase again...

Therefore, the braking process of a car equipped with ABS is actually a critical process of rolling friction - sliding friction - rolling friction, but we generally think that the braking process is rolling friction.

Sliding friction should be avoided as much as possible during the braking process, because the car is in a dangerous state of loss of control during the sliding process, which is prone to sideslip and lose steering ability, and will increase the braking distance.

There are three types of car brakes: service brake, emergency brake and parking brake, only the braking force is equal to static friction when parking brake.

What are you looking at!! Very unlevel question!! Don't do this question

If you were to go to outer space, how much would you weigh? 2) The weight becomes smaller, and the mass remains the same.

If an object weighs 30 N, then the mass of the object is 2).

When a car brakes and stops, it stops 1) moving friction.

1 becomes smaller 2Nothing is 3Moving friction.

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=.)

Select B (because the scale reads to the next digit, it is impossible to read it in place.)

So get in place.

Hence rounded to.

For this kind of question, it is possible to average (

Round. In addition, if the data is too biased, you have to discard the data with a large deviation.

Suppose the length of the railway is l, since the sound travels faster in steel than in air, the first sound comes from the rails of the railway, and the second time comes from the air, t steel = l 5200, t air = l 340, t air - t steel = 2s, l 340-l 5200 = 2s, and the solution of the equation can calculate that l is approximately equal to.

Solution: (1) Triboelectric electronization is the gain and loss of electrons outside the nucleus of two different substances, and the same substance will not cause electron gain and loss due to the same number of electrons outside the nucleus, so it will not produce triboelectric electronization;

2) Static electricity on chemical fiber clothes will attract dust;

3) Electrostatic printing, electrostatic spraying, electrostatic flocking, electrostatic precipitator and electrostatic sorting technology.

Multiple choice questions: The hands can rub and cause electricity, but the human body is a conductor and returns to the earth in an instant. 2. Q: Chemical fiber clothes rub electricity to attract dust. Use static electricity: large blankets are laid at the entrance of large shopping malls to generate electricity.