Physics Solve How to change this problem. Be as detailed as possible in your answers

AC Pair. Analysis:

When the CD terminal is short-circuited (C and D are directly connected together), R2 and R3 are connected in parallel and then connected in series with R1.

The equivalent resistance between ABs is Rab R1 [R2* R3 (R2 R3)].

i.e. rab 10 [120 * 40 (120 40)] 40 euro a pair.

When the AB terminal is short-circuited (A and B are directly connected together), R1 and R3 are connected in parallel and then connected in series with R2.

In this case, the equivalent resistance between CDs is rcd r2 [r1* r3 (r1 r3)].

i.e. rcd 120 [10 * 40 (10 40)] 128 euro item b wrong.

When AB is terminated with a power supply, there is no current passing through R2 (it is an equipotential body with equal potential at both ends), and current passes through R1 and R3 (R1 and R3 are connected in series), then the voltage of Cd is equal to the voltage of R3.

Get UCD U3 U source * R3 (R1 R3) 100 * 40 (10 40) 80 volts.

C pairs. When the CD is terminated with a power supply, there is no current passing through R1 (it is an equipotential body with equal potential at both ends), and the current passes through R2 and R3 (R2 and R3 are connected in series), then the voltage of AB is equal to the voltage of R3.

UAB U3 U source * R3 (R2 R3) 100 * 40 (120 40) 25 volts.

-d item is wrong.

Forget all about it!

Solution: The acceleration of the box can be decomposed into two directions, A1 vertically upwards and A2 horizontally to the right, respectively obtained by Newton's second law

f = ma2, and because, a1 = a2tan30°

The simultaneous solution is: f = root number 3 5mg, that is, the static friction between the box and the ground is the magnitude of the gravity it is subjected to (root number 3) 5

Conservation of momentum Initial momentum mb*v1 = final momentum (mb+mA)*v2 Calculate v2 that is, the final velocity of them together Just calculate the difference in kinetic energy mb*v1 square 2-(mb+ma)*v2 square 2 The first question will give the result The second question is better Calculate the relative displacement is The heat generated is also calculated in the first question Directly obtain f from q=fs and then use f mg to get the kinetic friction factor If you don't understand, please talk about it.

Pick D. When horizontal, there is no movement and the friction is 0If the angle increases, and the gravitational component is not enough to overcome the static friction, then f=mgsin, which increases at this time.

When the static friction is overcome, if the friction coefficient is , then f= mgcos, and the friction gradually decreases when the friction is slippery.

If the candidate does not let the static friction force be considered, then f= mgcos, which is always reduced.

At rest equilibrium.

f=mgsinα

Enlarged, F increased and the world was great.

When you start swiping.

f=μmgcosα

Enlarged, the absolute spring f decreased.

According to the title, it means branch d

1 Closing switch S, R1 short circuit, U = IR2 = 1A x 6 = 6V

2. Disconnect switch S, R1, R2 in series.

r total = u i = 6v

So r1 = r total -r2 = 15 -6 = 9

When v is maximum, the ball falls on the right corner, the horizontal displacement is diagonal, and the vertical displacement is 3h

v falls exactly in the middle of the net, the horizontal displacement is l1 2, and the vertical displacement is 3h-h=2h

d. The mass of the liquid remains unchanged, and the stressed area becomes smaller, so P1 increases;

The mass of the wood block remains the same, and the stressed area remains the same, so P2 remains the same.