The density is 600kg / m3, and the volume is 100cm3. The wood block is pulled into the water to calculate the gravity buoyancy and tension

The density is 600kg / m3, and the volume is 100cm3. The wood block is pulled into the water to calculate the gravity buoyancy and tension

Wood density p = 600kg / m ^ 3 = 0.6kg / DM ^ 3, Volume V = 100cm ^ 3 = 0.1dm ^ 3
Let t be the pulling force of the line to the block
Wood block gravity g = mg = PVG = (0.6kg / DM ^ 3) * (0.1dm ^ 3 (* (10N / kg) = 0.6N
Buoyancy f = gravity of drained water = pwater * VG = (1kg / DM ^ 3) * (0.1dm ^ 3 (* (10N / kg) = 1n
T=F-G=1-0.6=0.4N

The test center has carried out a comprehensive test on a certain type of electric vehicle. Under the condition of constant voltage DC charging of 220 V and 15 A, the electric vehicle can be fully charged in 5 hours. Under the condition of full load, the total mass of the vehicle and passengers is 1.5 T. under the condition of constant speed of 120 km / h (at this time, the total resistance of the vehicle is 0.022 times of the total weight of the vehicle and passengers), the vehicle can drive for 54 minutes, What is the energy efficiency of this type of electric vehicle?

The traction during driving is
F=1.5×1000×10×0.022N=330N
Work done during driving
W=Fvt=330×（120÷3.6）×54×60J=35640000J
The total charge energy is
Wtotal = uit = 220 × 15 × 5 × 3600j = 59400000j
So it's efficient
Y=35640000/59400000×100%=60%

The method of measuring the thickness of rectangular gold foil with density of ρ is designed by using millimeter scale and balance (with weight attached). (1) write out the main steps of the experiment and the physical quantities to be measured. (2) write out the expression of the thickness of gold foil to be measured

The main steps of the experiment are as follows: (1) measure the mass m of rectangular gold foil with balance; (2) measure the side length a and width b of rectangular gold foil with scale; calculate the volume of gold foil according to v = m ρ, and then calculate the thickness h of gold foil according to h = VAB. Expression: v = m ρ = ABH, so h = VAB = m ρ AB = mAb ρ, so the answer is: H = mAb ρ

Are dimes made of aluminum? Do dimes, dimes and dollar coins use the same metal

Strictly speaking, it can't be said that it's made of anything, because no matter what the dime, 50 cents or 1 yuan are made of alloy. The popular saying is that it's made of what's the main component. For example, if the dime is made of aluminum, it can't be said that it's wrong. But if you come to answer the question, this statement obviously won't score. For example, the fourth set of dime is made of aluminum magnesium alloy, The fifth set of Dimes is made of aluminum alloy. The landlord didn't say which set it is. You can find the following for yourself
List of the third set of RMB coins
Coupon type
Pattern
texture of material
diameter
Time of issue
positive
back
One dollar coin
National emblem, national name and year number
Great wall, denomination
Copper nickel alloy
thirty
1980.4.15
Fifty cents
National emblem and name
Gears, ears, denominations
Year number
Copper zinc alloy
twenty-six
1980.4.15
A dime
National emblem and name
Gears, ears, denominations
Year number
Copper zinc alloy
twenty-three
1980.4.15
A dime
National emblem and name
Gears, ears, denominations
Year number
Copper zinc alloy
twenty
1980.4.15
List of the fourth set of RMB coins
Coupon type
Pattern
texture of material
diameter
Time of issue
positive
back
One dollar coin
National emblem, national name, Chinese pinyin and year number
Peony, denomination
Nickel plating on steel core
25.0 mm
1992.6.1
Fifty cents
National emblem, national name and Chinese phonetic year
Plum blossom, denomination
Copper zinc alloy
20.5 mm
1992.6.1
A dime
National emblem, national name and Chinese phonetic year
Chrysanthemum, denomination
Aluminum magnesium alloy
22.5 mm
1992.6.1
List of the fifth set of RMB coins
Coupon type
Pattern
texture of material
diameter
Time of issue
positive
back
One dollar coin
Bank name, denomination, Pinyin and year number
Chrysanthemum
Nickel plating on steel core
25 mm
2000.10.16
Fifty cents
Bank name, denomination, Pinyin and year number
Lotus
Copper alloy plating on steel core
20.5 mm
2002.11.18
A dime
Bank name, denomination, Pinyin and year number
orchid
aluminium alloy
19 mm
2000.10.16