8th grade lower science urgent 8th grade lower science problems

Solution: (1) First find the area of a footprint s

By m= wax v= wax s h , h is the average thickness of the paraffin model.

s=m (wax h)=450g (

That is, the area of a footprint is 250 square centimeters. The cow has 4 legs, and the conclusion is that the bison has a contact area of 1000 square centimeters with the ground when standing on horizontal sand. (sqm).

2) By the relationship between pressure and pressure p=f s, so f=p s=. That is, the pressure of this bison on the sand when standing on the horizontal sand is 25000N.

3) The bison stands on the ground and is in equilibrium, so its pressure on the ground is equal to its gravity, so g=25000n.

From g = mg, m = g g g = 25000n 10n kg = 2500kg. The mass of this bison is 2500kg.

Equipped with nitrate and potassium x grams.

39+39 39 is equal to 39+39+14+16+16+16 x and find the value of x.

Set up to have x grams of ammonium nitrate.

14 42 equals 14+4+14+16+16+16 x and find the value of x.

60 kilometers per hour, 500 kilometers of fiber file search, how many hours does it take to ruin the calendar?

t =s/v =500/60≈

If the friction force on the armored personnel carrier is twice the weight of the object when it travels at 60 kilometers per hour, then how much friction does the armored personnel carrier use to travel [g takes 10n kg].

The gravity of the armored vehicle is g = mg = 16500 * 10 = 165000n friction f = g *

1.Time = Distance Speed = 500 60 = Hours.

2.Armored Qin told the balance to make the car gravity = mg = 16500 * 10 = 165000n

Friction = 165000*

kg key regret l Fan Youxian is right. So the draft grinds b

You can refer to.

1, C 2, C buoyancy is equal to gravity, so the pressure on the table does not change, the water depth is the same, so the pressure on the container does not change.

3. b The water has become deeper.

1. The car is front-wheel driven, and the car is only affected by friction in motion.

The rear wheels are subjected to resistance, preventing the car from moving forward, and the friction must be in the opposite direction to the power wheels.

2 Carbon dioxide has one carbon atom and two oxygen atoms Mass = minus 26 power Yu Zhou + minus 26 power * (16 12) * 2 = minus 12 power.

3. Increase the pressure to increase the pressure, and the friction will be greater when the pressure is large, so that the tractor is not easy to slip.

4.Density = mass volume Sphere volume = (4 3) cubic of pier.

Let the inner layer have a mass of m, then the outer layer is 2m, the radius of the inner layer is 3r, and the outer layer is r density A density B = (m 27r cube) (2m) r cube) =

The object immersed in the water is subject to the buoyancy of the water on it vertically upward, and the size of the buoyancy is equal to the gravity of the object to discharge the wide cavity of the water, and when the iron is all submerged in the water, Wang Huqi is subjected to the gravitational force of 100 cubic centimeters of water. Calculate the mass of this volume of water to get the buoyancy answer.

Hang the iron on the spring scale, you can directly calculate the mass of the iron and then change it to the arithmetic unit!