I have a physics problem, welcome netizens from all walks of life to try!

m = g g = kilogram.

p=m v=kilogram cubic meter》p water.

The object sinks to the bottom of the water.

Buoyancy f=pwater*g*v=1000*10*

Solution: m=g g=kilogram.

p = m v = kilogram cubic meter.

According to the formula, it can be obtained.

p>p water.

So: the object sinks in the water.

Buoyancy f=pwater*g*v=1000*10*

A: ...

Solution: Suppose it does not sink.

From p(density)=m v, it can be obtained.

p (density) = m v = 1200 kg cubic meters.

Because 1200 is greater than 1000

So the object will sink.

F float = PVG = 5n

Answer: The buoyancy is 5n

f=500*10^-6*10*1000=5n

If you make it into the shape of a boat, it may float for 6n, but if you sink it into the water and make a hole to get stuck underneath it without flooding, it will still meet the "object volume of 500 cubic centimeters", ......The answer might be any number from 5n to 6n (both 5n and 6n). Is it out of line?

3 cases of floating, levitating, sinking !! The formula is its own generation.

To find the density of the object, compare it with water first!

Will the object you hit move with the car?

If not: Solution: ft=mv=4000*50 Because there is no time in the condition, there is no solution. ）

If so, it is not possible to find the mass of the object because there is no mass in the condition.

The impact force of the car on the object is related to the length of the impact time. There is no impact time and it cannot be solved. It's like a person hitting a sponge, and the force on hitting a concrete floor is definitely not the same.

(1) Feasible According to the formula p=f s, f=ps When the suction cup happens to be out of the table, the tension of the spring dynamometer to the suction cup and the pressure of the atmosphere on the suction cup are exactly a pair of balance forces, so that f can be found and S can find the area by measuring the diameter of the contact surface, so that this design is completely feasible;

2) It cannot be calculated according to f=ps

f=10^5*5*10^-4=50n

The atmospheric pressure on the suction cup is about 50N, which far exceeds the measurement range of 0 5N of the spring dynamometer, so the device cannot successfully measure the value of atmospheric pressure

Keep the camera away from classmates and increase the length of the camera's camera obscura.

The camera moves away from the classmate, which increases the angle of view, but when the camera is away from the classmate, the distance between the camera and the object increases, and the distance from the object increases.

It can be simply seen that the distance between the object and the lens increases, so correspondingly, the distance between the optical screen (negative) and the lens should be shortened.

But there's no way for a camera to simply change the negative, which is the distance between the shells behind the camera.

Therefore, the lens is moved forward, (i.e., the length of the camera obscura) is indirectly shortened, so as to achieve the purpose of imaging on the negative.

So the answer is to stay away from growth.

When the motor shaft is temporarily stuck so that it cannot rotate, there is no output of mechanical energy, the motor is regarded as a pure resistance, and the r=2 ohms is obtained, and then rotates normally, and the current in the motor is; At this time, the thermal power dissipated by the resistor is determined by Joule's law, the total power is UI=, and the mechanical power is the total power minus the thermal power, so the efficiency is 90%.

Select D, you can analyze it in this way, the above situation occurs after the switch is closed, so it is impossible to short-circuit the socket, otherwise the lights will be all extinguished before, in the same way, if the lamp plug is short-circuited, the lamp should be plugged in when the lamp is plugged in, and if the lamp switch is short-circuited, it is equivalent to no switch, but the circuit is directly connected, and the lamp is not extinguished. Short circuit at the lamp head of the table lamp.

Moreover, the switch is turned on, which is equivalent to the direct connection of the wire, resulting in excessive current, tripping and other situations where the lights are all extinguished.

d Close the lamp switch, and turn off all the lights in the room to eliminate aShort circuit at socket bShort circuit at the lamp plug.

There is no short circuit in the switch.

d Because the indoor bulb is normal before plugging in the socket and closing the lamp switch, it can only be that there is a problem with the lamp head.