People's education press fifth grade volume II Vocabulary Manual 18 lessons accumulated over time

Brave, witty, upright, generous, square, dignified, aboveboard, fearless in the face of danger, stand up, calm, calm, quick witted, brave, brave, brave, brave, brave, brave, brave, brave and brave. Reading these words, it seems that Lin Xiangru and King Qin are fighting bravely in front of my eyes

Debate on the experimental textbook of compulsory education curriculum standard
Let's have a debate: in Lesson 17 of the compulsory education curriculum standard experimental textbook Chinese fifth grade volume I, "people shake their heads and sigh and walk away. They all think that the father is too sad because of the loss of his child. Is the father insane? We are right: the father is insane. Please give me some reference materials,

To choose the correct pronunciation for the Braille, just fill in the serial number
1. Shrinking: (1) from large to small or from long to short; (2) not extending or retracting after extending; (3) retreating
The shrinking of frugality () the shrinking of timidity () the shrinking of hand and foot () the shrinking of distance () the shrinking of heat and cold () the shrinking of retrenchment ()
2 absolutely: (1) cut off (2) completely no; exhausted (3) impassable; no way out (4) breath stop; death (5) unique; no one can catch up with (6) pole; the most (7) absolute
The one who is suffering from a terminal disease is the one who has never been able to survive. The one who has never been able to survive is the one who has never been able to be smart. The one who has run out of ammunition is the one who has never been able to survive. The one who has never been able to be angry is the one who has never been able to survive

The shrinking of frugality (1) the shrinking of hesitation (3) the shrinking of hands and feet (2) the shrinking of distance (1) the shrinking of heat and cold (1) the shrinking of retrenchment (1)
The one who is suffering from terminal illness (4) the one who is able to survive (3) the one who is extremely smart (5) the one who has run out of ammunition and food (1) the one who is unique (5) the one who is extremely indignant (4)

As shown in the figure, an object with mass m is placed on the spring and moves harmoniously with the spring in the vertical direction. When the amplitude is a, the maximum pressure of the object on the spring is 1.5 times of the gravity of the object. (1) what is the minimum elastic force of the object on the spring? (2) In order to keep the object from leaving the spring in vibration, how large is the amplitude?

(1) When the wood block moves to the lowest point, the spring force is the largest. At this time, according to Newton's second law, Fmax mg = ma, because Fmax = 1.5mg, so a = 0.5g. When the wood block moves to the highest point, the spring force is the smallest. At this time, according to Newton's second law, Mg Fmin = ma, the acceleration of the highest point and the lowest point is equal, that is, a = 0.5g, which is obtained by substituting Fmin = 12mg. (2) at the highest or lowest point: Ka = ma = 12mg, so the stiffness coefficient of the spring is k = mg2a. The object is in an overweight state below the equilibrium position, and it is impossible to leave the spring, only above the equilibrium position. To ensure that the object does not leave the spring during the vibration process, the acceleration of the object at the highest point is a = g, and the spring force is zero When the object just leaves the spring at the highest point, the restoring force is gravity, so: Mg = Ka ', then the amplitude a' = MGK = 2A. Answer: (1) the minimum elastic force of the object to the spring is 12mg; (2) to keep the object from leaving the spring in vibration, the amplitude cannot exceed 2A

How many degrees is 1kW. H equal to

1kW. H is one degree, 1kW. H is an academic term, and one degree is a common saying

Weigh the same object on the earth and the moon with a balance and a spring dynamometer. The result is ()
A. The readings of balance and spring dynamometer are the same. B. the readings of balance and spring dynamometer are the same. C. the readings of balance and spring dynamometer are different. D. the readings of balance and spring dynamometer are different, and the difference is very large

(1) If the balance works under the condition of lever balance, the mass of the object and the weight remain unchanged, and the gravity becomes the original 16. The lever is still balanced, so the measured mass remains unchanged, so the measurement results are the same. (2) the gravity of the object from the earth to the moon becomes the original 16, the tension of the object on the spring becomes the original 16, and the indication of the spring dynamometer becomes the original 16 16, so the measurement results are different

An isosceles triangle with a circumference of 80 cm, write out the functional relationship between the base and the waist length

Let the waist length be xcm and the bottom length be YCM
that
y=80-2x
(20＜x＜40)

When the car starts to move to the right, a small block with a mass of 2kg and an initial speed of 3.5m/s is placed on the left end of the car. The dynamic friction coefficient between the block and the car is 0.2. The following results are obtained: (1) assuming that the car is long enough, the water balance force is 8N, How long does it take to stop the relative movement with the car? What is the speed of the small block passing through 4S from the start of placing? (2) if the car is 49 / 40 in length, what is the water balance force in order to prevent the small block from sliding off the car?

1) There is friction between the car and the small block, they are subject to the same size and opposite direction of friction, friction F1 = M1 * g * 0.2, where M1 is the mass of the small block 2kg, G is the acceleration of gravity 10m / S ^ 2, F1 = 4N
After the time t, the velocity of the trolley and the small block is V1 = v0-t * F1 / M1 = 3.5-2t, V2 = t * (F1 + F) / m2 = 1.5T, f = 8N, V1 = V2, t = 1s, at this time, the velocity is V2 = 1.5m/s, and the velocity after 4 seconds is V3 = V2 + (4-T) * f / (M1 + m2) = 3.9m/s
The relative motion was stopped after 1 s, and the velocity was 3.9 m / s after 4 s
2) The final velocity is set as V, the horizontal force is f, the equations (3.5-v) / 2 = V / (F / 8 + 0.5) 2 and 0.5 are the friction acceleration of the car and small block, V ^ 2 / 2 (F / 8 + 0.5) + 49 / 40 = (3.5 ^ 2-V ^ 2) / 4 are listed, the solution of the equations is v = 2.1m/s, f = 20n, and the water balance force is 20n

1.6.9.9 what method is equal to 24?

9-1=8
9-6=3
3×8=24

The mass of the object is m, and the dynamic friction coefficient between the object and the horizontal plane is u. now, the object just moves in a straight line at a constant speed on the horizontal plane under the action of an oblique upward pulling force at an angle of θ with the horizontal direction. 1 find the size of the friction force; 2 find the size of the pulling force F

(1)
Fx=Fcosθ,Fy=Fsinθ
F = UN pressure = u (mg fsin θ)
(2)
f=Fx
u(mg-Fsinθ)=Fcosθ
F=umg/(cosθ+usinθ)

People's education press fifth grade volume II Vocabulary Manual 18 lessons accumulated over time