Use the spring dynamometer and measuring cylinder to do the experiment of measuring the density of a certain block and liquid, as shown in the figure. (known: g = 9.8n/kg; the scale unit of measuring cylinder is ml, that is cm3) calculate: (1) the buoyancy of the block immersed in the liquid; (2) the density of the liquid

Use the spring dynamometer and measuring cylinder to do the experiment of measuring the density of a certain block and liquid, as shown in the figure. (known: g = 9.8n/kg; the scale unit of measuring cylinder is ml, that is cm3) calculate: (1) the buoyancy of the block immersed in the liquid; (2) the density of the liquid

(1) (2) because the block is completely submerged, the volume of water discharged from the block is v row = V material = v2-v1 = 200ml-100ml = 100ml = 10-4m3, because f float = ρ GV row, so ρ liquid = f float GV row = 0.98n9.8n/kg × 10 − 4m3 = 1.0 × 103kg / m3

Watt: 1W = 1J / S
That kW: 1kW =?

1000J/S
K is a thousand
1W = 1J / s, which means that if one joule of work is done per second, the power is called one watt
KW, 1kW, that is to say, doing 1000 joules of work per second, 1kW = 1000j / s

What is the meaning of heat in junior high school physics

Temperature, internal energy and heat

A kind of wheeled bicycle howitzer has strong amphibious ability. It is propelled by two propellers installed on both sides of the rear of the vehicle. The wheeled bicycle howitzer has six wheels (g = 10N / kg) and weighs 16.5t
(1) If the contact area between each wheel and the ground is 0.02 m2, what is the pressure on the square when it is driving on the horizontal square?
(2) If the chariot is stationary on a horizontal plane, what is its buoyancy? What is the volume of water it discharges?
(3) When the chariot is still on the water, if the pressure of water is 1.5 × 104pa, what is the depth of this place?

1、
Pressure: F = g = mg = 16.5x1000kgx10n / kg = 165000n
Pressure: P = f / S = 165000n / 0.02m2 X6 = 1375000pa
2、
When floating, buoyancy is the same as gravity
F = g = 165000n
According to Archimedes principle:
F floating = ρ water GV drainage
V row = f float / ρ water G
＝165000N/1000kg/m³x10N/kg
=16.5m³
3、
P = ρ GH
H = P / ρ G
=15000Pa/1000kg/m³x10N/kg
=1.5m

I know a kind of wine is directly connected to the wire at both ends of the power supply, which is called short circuit
But I found that some nights are not called short circuit. Please explain to me. What else is also called short circuit?

Connect the conductor directly to both ends of the power supply, which is called short circuit. At this time, the current is very large, which will burn the power supply. For example, connect the ammeter directly to the two ends of the power supply, and the resistance of the ammeter is very small, which is this kind of short circuit. There is another kind of short circuit, which is to connect a resistor or both ends of a component in the circuit with a conductor

A. If we know that ρ A: ρ B = 3:4 and the volume VA: VB = 4:5, then the following conclusion is correct ()
A. A object must be hollow B. B object must be hollow C. two objects must be hollow D. two objects must be solid

It is known that the masses of two objects a and B are equal, that is, Ma = MB, ρ A: ρ B = 3:4, ∵ ρ = MV ∵ vavb = m ρ am ρ B = ρ B, ρ a = 43 ∵ the title "volume of two objects VA: VB = 4:5" ∵ B object must be hollow

Problems in preparing brine
Farmers often use salt water for seed selection, and the configuration data are as follows
Glass mass: 32.9g total mass of glass and brine: 101, volume of 1G brine: 62cc
The density of brine is--------
If you want to prepare 1.2g/cm3 brine, do you want to add salt or water to the brine above? How much?

101.1-32.9=68.2（g）； 68.2/62=1.1（g/cm3) ；
Salt is obviously needed
1.2 * 62 = 74.4 (g); need to add salt: 74.4-68.2 = 6.2 (g)

1. If the gravity of all objects on the earth suddenly disappears, what will our life be like
A person can drink water into his stomach
B water will flow lower
C launching a satellite doesn't require a rocket with high thrust
D people who hang in the air will fall
2. The following statement about the use of spring dynamometer is correct ()
A. the spring scale must be placed vertically without tilting
B any large force can be measured with a spring dynamometer
C when measuring the force, if the force direction of the spring dynamometer is along the axis of the spring
D before use, it is not necessary to check whether the pointer is at the 0 scale mark
3. The life activity of every living body needs metabolism. Suppose that the mass of material absorbed by the living body is m absorption and the mass of material discharged is m row, then for our middle school students, we are in the stage of growth and development. Under most normal circumstances, the relationship between M absorption and m row is ()
A. M suction > m row B. m suction = m row
C. M suction < m row D
I chose ACA
Let's explain the reasons

CCA

Junior high school physics relative speed how to seek? Please give examples, thank you

The meaning of relativity is to choose one of the objects as a reference and assume that it is immovable
For example, Xiao Ming walks eastward at the speed of 2m / s, and Xiao Li faces Xiao Ming at the speed of 3m / s. after one second, the distance between them is shortened by 5m, which is equivalent to taking Xiao Ming as a reference (assuming that he does not move), and Xiao Li walks 5m in one second at the speed of 5m / s
Opposite direction movement, velocity superposition, same direction movement, velocity subtraction

What do the letters mean in junior high school physics?

A amplitude
A acceleration
B magnetic field strength
C specific heat capacity and capacitance
C speed of light
D potential shift vector
D grating constant
E electric field strength
E electronic quantity
F force and method (capacitance unit)
F friction and vibration frequency
G gravity
G acceleration of gravity
H magnetization vector, H (inductance unit)
H height, depth, Planck constant
I current
I-dof
J Joule (unit of heat and energy), overlapping integral
K Kelvin (thermodynamic temperature unit)
M mass
N pressure / support
N refractive index
P electric power
P Pressure
Q heat and electricity
Q power
R resistance
R displacement, distance
S Journey
S seconds
T temperature, vibration period
T time
U voltage and potential
Vvolt (voltage unit)
V velocity
W work
X susceptibility
Z partition function