How does support count

1. The density of mercury is 13.6g/cm ^ 3, and the density of iron block is 7.9g/cm ^ 3. If the quantity of mercury is enough, the iron block will have v row = 13.6 / 7.9 * V immersed in mercury, but in fact, the depth of mercury is only 3cm, so the iron block still has a certain pressure on the bottom of the container.
the actual size of floating force on the iron block is: F floating = density of mercury * g * (3cm * 8cm * 8cm) = 26n

2.

F = UN (U is the dynamic friction coefficient)

resistance can be divided into many kinds of resistance. The calculation formula of air resistance FW is: FW = 1 / 16 · a · CW · V2 (kg), V is the driving speed, unit: M / s, a is the cross-sectional area of the vehicle, unit: M2: CW is the wind resistance coefficient

When the fluid flows in the pipe, the flow resistance will be increased e to the local obstruction of pipe fittings and valves, as well as the resistance caused by the expansion or rection of the flow section

extended data:

precautions:

1. Arm of force refers to the distance from the fulcrum to the action line of force (power or resistance), not from the fulcrum to the action point of force

When the direction of the force acting on the lever changes, the size of the force arm will also change

The arm of force is not necessarily on the lever

If the action line of the force passes through the fulcrum, the arm of force is zero

There are three steps to draw the force arm: find the fulcrum, draw the action line of the force, and draw the vertical line from the fulcrum to the action line of the force (sometimes it is necessary to extend the action line of the force in the forward or reverse direction)

3. The supporting force in junior high school physics, according to the motion state of the object, is calculated indirectly after the force analysis and according to the balance of the two forces
△ the supporting force in high school physics, according to the motion state of objects, after force analysis of multiple objects, one is: according to the balance of two forces, the supporting force is indirectly calculated; Second, according to Niu Er's law, support force can be calculated indirectly

I hope I can help you. If you have any questions, you can ask ~ ~ ~
I wish you progress in your study and make progress

4. If an object or a part to be examined keeps moving or stationary in a straight line at a constant speed, the supporting force is equal to the resultant force of all the other forces, and the direction is the same
otherwise, f = ma is used

5. What, the pressure is equal to the support force
only when the object is in equilibrium on the horizontal plane, the pressure is equal to the gravity. At this time, the pressure = the support force = the gravity

6. Work is the proct of force and displacement in the direction of force. The displacement in the direction of force is the displacement of the action point in the direction of force
if the supporting force has displacement in the direction, then the supporting force does work and can be substituted into the formula! If the point of action of supporting force does not change, no work will be done!

7. Normally, the supporting force is on the contact surface, but for convenience, it is drawn on the same point of action with gravity, that is, the geometric center. You can see the supporting force in the geometric center in your exercise book

8. The gravity of the lever

9. 1. Pressure and supporting force: when a body a applies a force perpendicular to the contact surface and pointing to B to another body B, then the force is pressure. Since the forces are mutual, the reaction force of body B to a is supporting force. That is to say, the pressure and supporting force are the same, but the direction is opposite
2. Gravity and supporting force: there is no relationship between the two forces themselves, but if the pressure of a on B is the same as that of gravity in the same direction, then the gravity is the same as that of supporting force in the opposite direction. Otherwise, we need to analyze and calculate the size and direction of the two according to the angle of force

10. First, calculate the pressure of water on the bottom of the container
formula F = P * s = PGHS
P is the pressure of water (formula P)= ρ According to the force and reaction, the pressure of water on the bottom of the container is equal to the supporting force of the bottom of the container