Physics questions for the second year of junior high school, about the physics questions for the sec

1、（h1+h2）×（d/2）²

2. (1) Echo ranging principle, s=v t

2) Time t1 when the sound is made, time t23) s=v (t2-t1) 2

3. Place an empty beaker on the right plate and adjust the game.

Question 1: (h1+h2)*(d 2).

Question 2: (1) The principle of sound propagating in a straight line in the air s=v*t2) The time when two echoes are heard after the sound is made t1, t2 is the time when the echo of the mountain wall on the left is heard, and the other is on the right

3）s=v*(t1+t2)/2

Question 3: Step 2: Place another empty beaker on the right plate and put a weight on the right plate to adjust the game.

Step 3: Read the weight and yard mass in the balance and the density of m (i.e. the net weight of the small stone) = m (v2-v1).

1.The volume of the bottle is v = (d 2 4 2) * (h1 + h2) echo ranging principle, s = v t

2) Time t1 when the sound is made, time t23) s=v (t2-t1) 2

3.Step 2: Place another empty beaker on the right plate and place a weight on the right plate to adjust the game.

Step 3: Read the weight and yard mass in the balance and the density of m (i.e. the net weight of the small stone) = m (v2-v1).

Question 1: A (40 3) resistor should be (in series) to emit light properly.

Question 2: The voltage ratio is (2:3).

In parallel circuits, the current ratio is (3:2).

Calorie ratio (3:2).

Question 3: The fault is (bulb disconnection).

This is because (the filament resistance of the bulb changes with the temperature, and when the brightness is different, the temperature of the filament is different, resulting in different resistance).

The actual power of the motor p1 = p amount * 60% = 45 *

One transportation time t=7min=420s

The velocity does not change, so the kinetic energy does not change, so the actual work = the potential energy increases: w = mgh = [60 * (15-8)] * 10 * (840-230) = 60 * 7 * 10 * 610

I suggest you can go to the new beacon to find a teacher, there are branches all over the country, and the teachers there are quite good.

Because the density of the object does not change, it is the density that determines whether the object floats or sinks, and the density of the object is greater than that of water, then the object sinks.

If the density of the object is less than that of water, then the object floats.

If the density of the object is equal to the water, then the object will be suspended.

So the object is suspended at the beginning, which means that its density is equal to water, and when it is cut, the density does not change, so it is still suspended.

The three objects have the same volume, but because of the different densities, one floats, one levitates, and one sinksSince it floats, the gravity of the water is the smallest, so the buoyancy of the ball A is the smallest, and the ball is the least buoyant, so it must be buoyant.

The ball experiences minimal buoyancy.

The gravity of the ball and the c-ball to drain the water is equal so the buoyancy is equal.

3. The density remains unchanged, all suspended, and D is selected

4. Choose D, the V row of the BC ball is the same, so the buoyancy is equal.