Thirteen Physics Questions!! Thank you, hurry

When the switch is closed, S is at the A terminal, the rheostat is connected in parallel with the lamp, and the lamp emits light normally, indicating that the power supply voltage: U 18V

Current of the lamp: i p u 18 18 1a

So the current of the rheostat is: i'＝

Its maximum resistance: r u i'＝18/

When the switch is disconnected, the rheostat is connected to the circuit 3 4, that is: the access circuit is 12 3 4 9

Current: i 15 9 5a 3

Voltage of the lamp: U lamp 18 15 3V

Actual power: P ui 3 5 3 5w

I don't know what to ask.

Solution: When P is at the A end, the sliding rheostat R is connected in parallel with the bulb L, the ammeter measures the current on the main road, I total =, the bulb L emits light normally, the voltage at both ends of the bulb is UL=18V, then the power supply voltage U=UR=UL=18V

The current through the bulb il=p ul=1a

The resistance of the bulb rl=ul il=18

The current of the rheostat is ir = i total -il=

The resistance value of the rheostat r = your ir = 18 = 12 When the switch S is disconnected and P moves 3AB 4 length from terminal A, the bulb and the rheostat r are connected in series to the circuit, and the resistance value of the rheostat.

r‘=12*3/4ω=9ω

Then the power of the bulb p'=[u (r'+rl)]^2*rl=8w

Solution: The velocity direction of the diamond cutter is decomposed into the direction of the knife and the direction perpendicular to the direction of progress. Then by forming a right-angled triangle, it can be obtained:

cos@=2/10=1/5

arccos(1/5)

Therefore, the angle between the direction of the knife and the direction of movement of the glass plate is arccos(1 5), and the velocity of the vertical glass plate forward direction can be obtained through the right triangle is:

v= (10 2-2 2)=4 6 m s, so the cutting time is:

t=s/v=9/(4√6)

3√6)/8 s

s

This question can be used to make a rough V-T diagram to simplify the thinking process.

The answer is: b 2

The masses of the two objects A and B are equal, the density of the two objects A and B is A 4 B, if they are both solid, then Vb 4Va, and the actual volume relation is Vb 6Va, so B is hollow, and the hollow volume is 6VA-4VA=2VA

t=, the two waves advance and both propagate to point m, at which point m begins to vibrate and goes downward. The two waves are superimposed, A' becomes 4cm, and then after 1 4 periods, M reaches the trough, and the displacement is, A is right and B is wrong.

The particle only vibrates up and down in the equilibrium position, c is wrong.

The vibration direction of each particle is downward, and D is wrong.

Descending at a constant speed indicates that the component of gravity is balanced with the frictional force. That is, the friction force is f1=mg*sino; When sliding upwards at a constant speed, the block is also balanced. Then at this time there is:

2*mg*sinos=f*cos (friction + component of the gravity of the block = f*cos) gives f=2mgsino cos so when =0°, f is the smallest, which is 2mgsinoThe frictional force is mg*sinoThe o in the above formula is the wooden wedge inclination is completed, and the work is over!

In the end, you got the velocity right, and the direct momentum is conserved.

The kinetic energy lost by the wooden block is actually e1=1 2m(vt -v0), and the kinetic energy increased by the wooden board e2=1 2mv0

The internal energy is e= e1- e2

Note the displacement relationship in red.

vb=va*cos53=

hb = (last question: the kinetic energy of a increases, and the velocity increases: va.)'>1m/s

Decompose the velocity of a, the velocity along the direction of the rod is and the velocity, one along the direction of the rope, one perpendicular to the direction of the rope, find, vb = v rope = vacos53 =

The gravitational potential energy of b is converted into the kinetic energy of ab, the mechanical energy of the system is conserved, the kinetic energy of ab increases, and the velocity of a is greater than 1m s

1. Fractions are not allowed in physics.

2. A force is an accelerated movement.

Let the current be i and the resistance be r at 3V, and use Ohm's law to set a system of binary linear equations. 3=IR,, the rest is the math problem.

Since r is constant, then r=u1 i and r=u2 i+, so we can get u1 i=u2 i+, so we get i=3 4, and then r=u1 i=4

Let the current be i and the resistance be r, then according to Ohm's law, we can list the system of equations:

ir=3，i+。

The solution is r= 4 ohms.