Physics fill in the blank question 3, a physics multiple choice question

The kinetic energy is equal to the product of the mass of the object divided by 2 by the square of its velocity, i.e., the kinetic energy of the same object is proportional to the square of its velocity;

The gravitational potential energy is numerically equal to the work done by gravity on the object, and if gravity does positive work, the gravitational potential energy decreases and increases conversely.

From the above, it can be seen that the velocity of the spacecraft increases continuously when it lifts off, so the kinetic energy increases. When the spacecraft ascends (approximately seen as a straight line in a short distance), the direction of gravity is opposite to the direction of its displacement, and the gravitational potential energy increases due to w=fscosa, and the gravity does negative work on the spacecraft.

The mechanical energy is equal to the sum of the kinetic energy and the gravitational potential energy, which also increases.

Note: In felice62, "the gravitational potential energy increases when the altitude increases", but according to the formula of gravitational potential energy ep=mgh, although the height of the spacecraft increases when it rises, the gravitational acceleration g decreases at the same time, so it cannot be said that the gravitational potential energy increases when the height h increases according to ep=mgh.

Enlarge, enlarge.

Kinetic energy is 1 2 times mass and then multiplied by the square of the velocity, the mass is generally unchanged, so the speed becomes faster is the kinetic energy increases, and the velocity decreases the kinetic energy; Mechanical energy is kinetic energy plus potential energy, only in the case of gravity workmanship mechanical energy is conserved, in the case of external force workmanship is not conserved, to specifically analyze all external force workmanship to add up, look at the positive or negative, you will know whether to increase or decrease.

Increase Increase The spaceship must have a speed greater than kilometers per second in order to lift off, so the spacecraft must increase its mechanical energy and its kinetic energy in order to increase its speed.

Big, big. The mass of the kinetic energy root is directly proportional to the velocity, and these two quantities become larger, and the kinetic energy becomes larger. Mechanical energy is the sum of kinetic energy and potential energy.

Increase: Increase.

As the velocity increases, the kinetic energy increases, and so does the mechanical energy.

are all increasing. The increased kinetic energy and potential energy are transformed by the chemical energy of the fuel. For the same object, the kinetic energy increases when the velocity increases, and the gravitational potential energy increases when the altitude increases. Mechanical energy is the sum of kinetic and potential energy, and of course it is also increasing.

Minish; Enlarge.

First of all, the rocket has to overcome the gravitational force to do work, its mechanical energy decreases, and then the kinetic energy decreases due to the increase in altitude and the gravitational potential energy increases.

ab is clearly wrong.

When AB does a uniform acceleration linear motion.

A constant velocity change is generated.

Produces a uniform change in the strength of the magnetic field.

So that the right end is equivalent to a DC power supply, IR is not equal to 0, IC is equal to 0, D is correct.

When AB moves in simple harmony, alternating current is generated, so capacitor C is constantly charged and discharged.

Therefore, IR and IC are not equal to 0, so C is also correct.

(1) Smaller.

2) Between 1 meter (excluding 1 meter) and 1 mm Straight line (3) Extraterrestrial satellite 3

4) Fiber optic cable.

(1) The frequency of radio waves (large), the amount of information transmitted in the same time (more).

2) Microwave communication: the wavelength of microwave is between (, the frequency is between 30mhz-300000mhz, the nature is close to light waves, roughly along (straight line) propagation, can not be diffracted around the surface, therefore, it is necessary to build a microwave relay station every 50km or so.

3) Satellite communication: use (artificial earth satellite) as a microwave relay station. Global communication can be achieved by evenly distributing (three) synchronous communication satellites around the earth. Geostationary communication satellites are stationary relative to the Earth.

4) The characteristics of laser --- high brightness, good parallelism and good monochromaticity. The laser light used for communication needs to propagate in the (optical fiber) in the mode of total reflection. Optical fibers are very thin glass filaments.

I can't read the question clearly. Can you describe it in words?

f = ps = 1×105

pa ×5× 10-4

The M 250N>5N exceeds the range of the spring dynamometer, so it is not too prudent to do so.

The image is an S-T image, so the speed of car B is 10 5 = 2 (m s).

At the fifth second, the corresponding s of car B is 10m

For car B, car A is in motion (because car B is moving at a constant speed relative to the ground, car A is stationary).

B's speed v=10 5=2m s, B is driving at a constant speed, and A is stationary.

B travels a distance of 2 meters per second, so the distance traveled in the 5th second is 2 meters.

Taking B as a reference, that is, if B is regarded as stationary, A is moving at a uniform speed, and the direction is the opposite direction of B's motion.

The maximum static friction force is used as the centripetal force.

There is a centripetal force formula f=mv r, get.

mg 10 = mv 400, so v = 20 ms cannot exceed 20 m s

According to the idea of infinite segmentation, the magnitude of the elastic force should be equal to the area of the elastic image and the horizontal axis in the image of Zhimin Yi.

Therefore, the elastic force does the work = 1n*, the elastic force does the negative work, and the potential energy of the ruler calendar bullet is increased.

When the spring is compressed, the elastic force does work = 1n*, the elastic force does negative work, and the elastic potential energy increases.

1. For the same substance, the larger the volume, the greater the mass, and the mass is proportional to the volume.

2. There will be differences in the quality of different substances of the same volume.

1.The mass of A is 10g, and the volume is doubled, and the mass increases by a multiple of the response.

2.A has twice as much mass as B.