Please help solve a physics problem! Urgent!!

1 What is the maximum static friction between an object and the ground? - 190n basis: To make it move, a minimum of 190n horizontal thrust is used——— 190n2 What is the sliding friction between the object and the ground?

180N basis: If only 180N horizontal thrust is needed to maintain the uniform motion of the object after moving——— at this time, it is in a balanced state and the force is balanced. Horizontal thrust and friction.

then the frictional force is equal to the thrust force.

3 When an object is moved by a horizontal thrust of 250N, how much friction is experienced on the object? ——180n

Basis: Once the object is in motion, it is subjected to sliding friction. The sliding friction is only related to the roughness of the contact surface and the positive pressure on the contact surface.

In this problem, since on level ground, the positive pressure is equal to the gravitational force, which is unchanged. It is all ground, and there is no special explanation, it is considered that the roughness is unchanged, so it is judged that the sliding friction is unchanged, and it is still 180N. At this time, the force on the object in the horizontal direction is no longer balanced, and it will accelerate its motion.

But no matter how you move, as long as you don't stop, the sliding friction is 180N

1.The maximum static friction is 190N

2.The sliding friction is 180N, and the coefficient of friction = 180 600=

3.The friction force is still 180N, and the object accelerates.

1 m = p * v = 1000 kg cubic meter * cubic meter = 3 kg.

2 e = c * m * t = 1 joule * 3000 g * (100-20) = joules.

Q=P*TT=Q P=E 840 Watts = Seconds = Minutes.

3 p=u*i=u^2/r

r = u 2 p rated = (u * actual.

p actual = p rated * watts.

1. The density of water can be found to be 3 kg.

2. The heat absorbed by boiling water is Q=CM(T-To)=PThe time can be found in seconds.

3. Use p amount = U2 R to find the R pot, P real = u real 2 R pot can be found.

(1) Work done by gravity: mgh = mgl - mglcos 30 ° = mgl (1-cos30 °) = root number 3) 2] = 2 (2 - root number 3).

The displacement in the direction of tension is 0, so the work done by tension is 0

2) The kinetic energy at the beginning is 0, and the work done by gravity is equal to the increase of kinetic energy, so the kinetic energy at the lowest point is: 2 (2 - root number 3).

1/2mv^2=

v 2 = v (3) lowest point tension:

f=mv^2/l+mg=

(1) The work done by gravity is the vertical displacement * gravity.

w=(2-root-number3)*

Tension does not do work (because there is no way to phase displace).

2) Kinetic energy, i.e., gravity does work.

w=e=1 2*square, v can be found

3) Circular motion, according to the formula.

Formula 2 can be found n

(1) Gravity: w=mgh= 4-2 3 joules according to the angle h=(2-3).

Tension: Since it is a circular motion, tension does not do work.

2) According to the kinetic energy theorem: w = ek = 4-2 3 joules 1 2 * square = 4-2 3 joules.

v=...3) F direction = f zhang - g = m * (v square 2) = square 2

The following symbols are explained: l is the length of the rope, m is the mass of the ball, h is the height difference, r is the radius of rotation which is also equal to l....(1).Because the tension makes the end perpendicular to the velocity, no work is done, and gravity does work as:

mgh=mg(l-sin30)…(2).In this process, the gravitational potential energy is all converted into kinetic energy: (as in (1)), and v is the velocity from 1 2mv (squared) = mgh(3) In this process can be regarded as circular motion:

f (tension) - mg (gravity) = f (centripetal force) = mv (squared) r......Bring in the numbers yourself and do the math! If it doesn't work, I can't help it....

Question 9: "45%" (vol) is the volume percentage of alcohol, that is, 45% alcohol and 55% water in a bottle of wine. Let the volume of this bottle of wine be v, then density = total mass Total volume = alcohol mass + water mass Alcohol volume + water volume = alcohol density * alcohol volume + water density * water volume Alcohol volume + water volume = 800kg m3 * 45%v + * 55%v 45%v + 55%v = 910kg m3 that is, grams per cubic centimeter.

When you make it, the text in the formula is represented by the corresponding letters, and here the method uses subscripts, so it is represented by words.

Question 11: Gold density = gold mass Gold volume =

19,200kg m3 is gram cubic centimeter, while pure gold has a density of gram cubic centimeter.

Explain 11 questions: gold density = gold mass gold volume, gold mass is, and gold volume is equal to the volume of overflow water after the necklace is put into an empty bottle filled with water, that is, the mass of overflow water divided by the density of overflow water, so use (to represent the gold volume, this step is the most difficult to understand, you look at it more, you will understand, in addition, these two questions are not difficult, you need to understand.

The necklace is placed in an empty bottle filled with water The weight of the water and the empty bottle at this time is the weight of the empty bottle when the empty bottle is filled The weight of the water and the empty bottle is.

It can be known that the weight of the water reduced by putting it into the necklace is.

The density of the water. The volume of water reduced is.

The density of the necklace is.