The calculation of velocity and density in physics in the second year of junior high school includes

The year is the Year of the Pig in the lunar calendar, Lan Lan's house has a baby pig ornament, placed on the horizontal table, the baby pig is solid, Lan Lan wanted to know what substance it was made of, so he managed to measure its mass is, the volume is 2 10-4m3, and the total area of the pig's feet on the ground is 4cm2. (g takes l0n kg).

1) Determine what kind of substance the baby pig may be made of by calculating and looking up the table.

2) What is the pressure of a baby pig on the table?

1) The density of the baby pig is: =m v=

Check the table: Baby pigs may be made of copper.

2) The pressure on the desktop is: f=g=mg=

Then the pressure on the desktop is: p=f s=

2.In the week of "May 1st", Zheng Zheng and his mother traveled to Wuxi and bought a Yixing teapot, she heard that the Yixing teapot was made of Yixing's unique clay material, and she wanted to know the density of this material. So she measured the mass of the lid with a scale, put the lid into the overflow cup filled with water, and measured the mass of the overflow water.

1) Could you please help us calculate the density of this material?

2) If the mass of the entire empty teapot is measured to be 159g, what is the volume of the material used in the teapot?

Solution: v lid = v water = m water water = mud = m lid v lid = or v pot = m pot mud = 159g (or.

3.A person from A to B, first ride a bicycle at a speed of 8 km h to pass through the flat road, and then at a speed of 4 km h uphill to B, share, return, first go downhill at a speed of 12 km h, and then return to A at a speed of 9 km h through the flat road, share 55 minutes, find the distance between A and B.

Set up flat road L1 and slope road L2

Then: l1 8+l2 4=

l1/12+l2/9=55/60

Get: l1 = 6 km l 2 = 3 km

l =9km

A car is driving at a constant speed, honking its horn in front of it, and an echo is heard as it passes. It is known that the speed of sound in the air is 340m s, and the speed of the car is found.

Set the velocity to vs=v*t 2

v=12

Question: 1. There is a mountain in front of the car, the car is driving at a constant speed of 12m s, the car honks, after 2s, the driver hears the echo, how far is the car from the mountain at this time? （v＝340m/s).

Answer: (340*2+12*2) 2-24=328 Questions: 2. There are two students who want to measure the length of a railroad track.

An area in the upper reaches of the Yangtze River flows 25 million tons of soil into the river every year, which is equivalent to how many square meters of 40cm thick land is lost in the region every year? (The average density of the soil is.)

It stretches on the road around the island in Xiamen"Never Stop" group carving, the scene of the marathon will always be fixed on the most beautiful track in the world, the size of the sculpture is about the same as a real person, if its density is 8000kg cubic meters, the mass of each statue is about ().

a 5kg b50kg c500kg d5000kg

Final Physics Review (Density Calculation Questions).

An ice cube with a mass of 9 kg and a density of kg m3 Find the volume of an ice cube? After the ice cube melts into water, the body.

How big is it? 2.The mass of the metal is 6750 kilograms, and the volume is m3What is the density of this piece of metal? If this piece of metal is truncated by 2 3, what is the density of the remaining part? 3.The density of iron is 3 kg m3, and what is the mass of 20 dm3 iron blocks?

4 When a bottle is filled with water, the total mass is kilograms. When filled with kerosene, the total mass is kilograms. Find the quality of the empty bottles.?

5. Knowing the density of ice, then after a piece of ice with a volume of 80 cm3 is melted into water, what is the mass of water g, and what is the volume of water cm3

6 A park to cast a bronze statue, first use wood to make a wooden mold with the same size as the bronze statue, now the mass of the wooden mold is measured to be 63kg, ( wood =, aluminum = Q: how many kilograms of copper do you need to cast this bronze statue?

7.There is a commemorative coin whose mass is grams, and to measure its volume, it is placed in a graduated cylinder filled with water, and the mass of the spilled water is measured to be 1 8 grams. (1) Find the metal density of the commemorative coin; (2) Say the name of this metal.

An aluminum ball has a volume of 20 cubic centimeters and a mass of 27 grams.

Method 1: Find the actual density: =m v=27g 20cm3=<, so it is hollow.

Method 2: Find the mass: Assuming that this ball is solid, the mass should be m=v=>27g, so it is hollow. (For the same large iron ball, my solid mass is 54g, and the title is only 27g, indicating that it is hollow).

Method 3: Find the volume: Assuming that the ball is solid, the volume should be v=m =27g (<20dm3, so it is hollow.

Why can I only make a small iron ball of 10cm3 with the same quality of iron, but I can make a large iron ball of 20cm3 in the title, which means that it is hollow, hehe......）

Seed selection with brine requires a density of 1100kg m3, and is now equipped with 50dm3 of brine. Weighing its mass of 60kg, does such water meet the requirements? If not, should salt or water be added, and how much?

Solution: 60kg divided by 1200kg m3 is greater than the required density, add water.

Let the volume of added water be xm3, then the mass of water is 1000xkg, 60+1000x)kg (, find x, multiply by 1000 is the mass of water.

The mass of a bundle of copper wire is kilograms, and the cross-sectional area of copper wire is 2 square millimeters, what is the length of this bundle of copper wire? (p is the density, p copper = 8900 kg cubic meters).

Solution: p=m v first find v=

If half of the block is submerged in water, the spring dynamometer will read.

1) What is the density of such a block?

2) Does this type of block float up or down when put in mercury? Why?

3) If the block is completely submerged in kerosene, what will be the reading of the spring dynamometer? Density = mass volume.

Gravity = mass.

Mass = gravity

Because half of the block is submerged in water, the buoyancy = the density of the water x the volume of the water discharged, and the buoyancy = is known from the dynamometer reading

Volume of drained water = buoyancy The density of the water.

The density of water is a known quantity, and the volume of water discharged is obtained.

The volume of drained water x2 is equal to the volume of the block.

At this point, the density of the block can be found.

In mercury, the density of the two is compared, and the density of the block is greater than the density of the mercury, that is, the sinking is reversed.

All immersed in kerosene according to the buoyancy formula f = kerosene density x block volume, and then used to read the dynamometer.

ρ=m/v

420g/500cm^3

Not up to standard: Too much water.

Suppose a milliliter of alcohol is added.

Then the mass of alcohol added is grams.

m/v (420g+

Solution a = 500ml

An additional 500ml of alcohol should be added.

1 When a bottle is filled with oil, the total mass is, when it is filled with water, the total mass is, the mass of water is, find the density of oil 2 The mass of object A is 3 times that of object B, so that the ratio of the volume of objects A and B is 3:2, find the ratio of the density of objects A and B 3 The vial is filled with water and the mass is weighed as 210g, if a 45g metal block is placed in the bottle and then filled with water, the mass is weighed as 251g, and the density of the metal block is found 4 The densities of the two metals are respectively , The two metals of the same mass are alloyed and the density of the alloy is proved to be (assuming the volume does not change during mixing).