Middle school science questions pull different versions of teaching

Ostrich eggs (an egg is a cell).

Maple poplar and elm.

Lilies and tulips.

Ash and almond trees.

Dandelion and so on.

The fruits of many plants also have wings, and with their wings, they become "flying generals". The flight equipment of the plant is quite good, some have wings or wing membranes, some have needles, and some have feathers or fluff. With the fruits and seeds of flying equipment, you can fly with the wind to distant places and settle down.

There are many species of plants that have wings on their fruits or seeds. Maple poplars and elms produce yellow-green flowers in early summer and bear fruit in autumn, the fruit of the maple poplar tree has two wings, one left and one right, and together with the wind, they fly into the sky like nimble swallows. The elm tree has two membranes on its wings, and when the wind blows, they leave the elm tree and fly far away with the wind.

The seeds of lilies and tulips themselves grow into thin flakes and glide like gliders in the wind; The seeds of the ash tree and the stink tree have wing-like protrusions, like long-winged fighter planes; The dandelion seed has a crested hair on its head, and the wind drags it high, and the achenes hang down like a parachute; The feather grass that grows on the grassland, with feathers on the top of the fruit, is blown far away by the wind, and when the wind stops, it falls vertically like a parachute, and the fruit rotates and inserts itself into the soil. Scientists have observed and studied the fruits and seeds of wings, and found that the winged fruits of birch trees can fly up to 1,000 meters away; Spruce seeds, which resemble the wings of a ship's sails, can fly up to 10 kilometers away. Some plant seeds themselves are very light, and when the wind blows, they fly around like wings, such as the seeds of plum grass, which are only three hundredths of a hundred thousand grams each, and the seeds of velvet orchids are even lighter, weighing only one hundred thousand grams each, and when the breeze blows, they will fly far, far away.

Animal egg cells.

Maple poplar fruits, dandelions, showa grasses, lilies and tulips.

Ash trees and stinky trees, hungry velvet words, all ah.

A few upstairs are really stupid.,Junior high school knowledge eh@!

The largest cells are (in the human body) (egg cells).

Plants with wings on their fruits are: maple poplar, elm, lily, tulip, ash tree, and almond tree.

Dandelion (pick two!)

The soft daughter cells of animals are the largest.

The largest cell.

It's an ostrich egg.

This is definitely it.

It's an ostrich egg!

The problem is to make sound waves travel the same distance in air and solid at the same time, and tell you the time difference to find this distance.

Make a list of equations and solve them.

x/v1-x/v2=t

i.e. x 340 - x 5200 = 2x=

Let the length of this section of railway be l, then.

l v empty) (l v iron) t (time difference) i.e. (l 340) (l 5200) 2 The length of the railway is l meters.

There are many kinds, such as the Shanghai Science and Technology Publishing House (Shanghai Science and Technology Press), the Western Normal University version (Southwest Normal University Edition), the Beijing Normal University version, the taught version, the Cantonese education version, the Suke version, a lot, you check the local teaching information, see what version it is!

A: From the diagram, we can see that the movement of the elevator is divided into three phases.

0-4s is the first stage, at this time the elevator does a uniform acceleration movement, the acceleration is meters per square second 4s-64s This 60s does a uniform motion, and the speed is.

64s-70s The 6s do a uniform deceleration movement, and the acceleration is 1 meter per square second, and the elevator moves at a constant speed.

h1 = vt = m.

Uniform motion tensile force f1 = mg = 10000n (g to obtain 10) work w1 = f1h1 = 480000j

2. The average speed is equal to.

Then the height of the acceleration phase is h2 = meters.

The work of the acceleration phase w2=f2h2=f2

f2=20000n

The problem is a bit problematic, according to Newton's laws of motion, the calculation result is not this result, you can only do it according to the title)

3. The average power is equal to the total power time.

8000w hope it helps you.

Solution: (1) the elevator in the constant speed stage V1, T1 60s, the elevator in the constant speed movement stage of the rising height h1=v1t1=;

Pull force f1 work w1 = f1h1 6000n 48m ;

2) the average velocity of the uniform acceleration phase v2 (;

Motor tension f2 w2s2 in uniform acceleration stage ;

3）w=w1+w2=；

The average power of the pulling force of the motor is P=WT=299520J64S=4680W;

Let the time of overtaking in the same direction be t1, the speed of car A is v1=15m s, the speed of car B is v2=11m s, the reverse wrong time is t2, car A is long l1=120m, and car B is long l2.

So: t1=(l1+l2) (v1-v2)t2=(l1+l2) (v1+v2).

t1-t2=55s

Junction on the bilison, l2 = 140m