Density and buoyancy The volume of an object is 0.5 cubic decimeter, and it weighs 4N. When it is immersed in water, will it sink or float or float

Density and buoyancy The volume of an object is 0.5 cubic decimeter, and it weighs 4N. When it is immersed in water, will it sink or float or float

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The weight is 4N, and the mass can be calculated as M = g / g = 4 / 10 = 0.4KG = 400g, v = 0.5 cubic decimeter = 500 cubic centimeter,
So density = m / v = 400 / 500 = 0.8g/cc, less than the density of water 1g / cc, so it floats up

Buoyancy formula. Tells you that the spring dynamometer in the air is a lot of N, the water is a lot of N, let you find buoyancy, body bulk density
Immerse an object in half, tell you the density of the liquid, find the indication of the spring dynamometer. What I want is the method to solve these problems!

In this problem, f-floating = g gravity in air - G gravity in water. After finding f-floating, according to f-floating = liquid density times G times the volume immersed in water. G is generally 9.8n/kg or 10N / kg. If the liquid density is known, the volume of the object immersed in liquid can be calculated

In the following physical quantities, which one should consider the size and direction? A mass, force B mass, length c current, length d current, force

D
Mass has only size and no direction,
Length has only size, no direction
The current has size and direction
Force has size and direction,

When to use x = v0t + 1 / 2at ^ 2, when to use v ^ 2-v0 ^ 2 = 2aX, and when to use V-T image

The application scope of the first two is uniform acceleration linear motion
It's just that the conditions are different
The final V-T image can be used for any motion
(but calculus is the difficult subject)
When we know the initial velocity V0, acceleration a, time t, we use the first one
When we know the initial velocity V0, the final velocity V, the acceleration a, we use the second one

Senior one physics v = V0 + at, x = v0t + 1 / 2at ^ 2, V ^ 2-v0 ^ 2 = 2aX, x = (V + V0) / 2 × T. when are these four formulas most convenient to use and what are they used for? If you can, please give me some examples, you will get good comments

There are four physical quantities: velocity, time, acceleration and displacement. The first formula doesn't use displacement to calculate velocity. When there is no displacement involved in the topic, it's easier to use it or other quantities to calculate velocity. The second formula uses all quantities to calculate displacement. That is to say, the conditions of the topic are very sufficient. The basic quantities of variable velocity motion are clear

How to remove t from v = V0 + at and x = V0 + 1 / 2at square to get V square - V0 = 2aX?
(0 is subscript)

t=(v-v0)/a
Simplify from generation to generation

In v = VO + at and x = VO + 1 / 2A T, the relationship between displacement X and velocity V can be directly obtained by eliminating t from the two formulas, and then v-vo = 2aX can be obtained. Who can write down the detailed steps for me

This is the formula for calculating the distance of high school acceleration, but you have made a little mistake in the question x = VOT + 1 / 2at ^ 2. Only in this way can you deduce the result you want t = (v-vo) / A. substituting x = VOT + 1 / 2at ^ 2, you can simplify the v-vo = 2aX

How to calculate the acceleration when the displacement formula s = v0t + 1 / 2at2 slows down at a constant speed?
such as
After braking, the car driving at the speed of 18m / s decelerates evenly and advances 36m in 3S. Calculate the acceleration of the car
How to find? If you replace the formula, you get a positive number. Shouldn't it be a negative number?

1/2at^2=36-18*3=-12
a=-3/8

Is the formula V at = 0 in the last few seconds or V at = 0 in the last few seconds

V = V0 + at
Here V0 is the initial velocity
V=X/T
It is used to calculate the average velocity of a section of displacement,
If you want the speed at the end of the second, you can't use this

Is the formula v = V0 + at used to calculate the instantaneous velocity of non-uniform linear motion?
If not, is it for instantaneous velocity?
If not, what is it for?
How to calculate instantaneous velocity and instantaneous velocity of non-uniform linear motion?

Vt = VO + at is the velocity formula of uniform linear motion. VO is the velocity at the time of T = 0. At is the velocity variation within time T. VT is the instantaneous velocity at time T. If a is calculated as a vector, that is to say, the sign of acceleration direction before a is also brought into the formula, then the formula is finally solved