1. Connect an electrical appliance marked "220V44W" into the circuit of 1 10V, and the actual power is _ _ _ _ (assuming its resistance remains unchanged).

2. If the voltage across the constant resistance increases from 8V to 10V, the current flowing through it will change by 0.2 A accordingly, and the constant resistance says that the change of power consumption is: A.0.4WB.2.8WC.3.6WD cannot be determined. [C]

3. Put the raw rubber block with a volume of 50 cm 3 and a mass of 48 g into enough water and let it stand, and the buoyancy of water on it will be _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

[g = 10N/kg] [0.48N]

4. A classmate pushed a box weighing 100 cattle 20 meters along the horizontal plane. What he did to the box was:

1000 angle C.2000 angle D.3000 angle [b]

5. Pull a 200-Newton object to the right with a force of 50 Newton to move in a straight line at a uniform speed on the horizontal ground, then the friction force on the object is

Cattle. [50 cows]

6. The rated power of the matching motor of a water pump is 2200 watts, its coil resistance is 3 ohms, and the current working under the rated voltage of 220V is 10A, so the heat generated by the coil in one second is A. 16 100 joules B.2200 joules C. 1900 joules.

300 joules

7. The maximum pressure that a brick can bear is 4.9× 105 Pa. If this brick is used to build a wall, how high can the wall be built? [The density of brick is: 2.45× 103kg/m3, ignoring the gravity and thickness of putty in brick joints, and g is 10N/kg] [20m]

8. As shown in the figure, try to make its power arm and resistance arm. If G= 100 N, OA = 2m, OB = 1m are known,

When the lever is balanced, what is the force F 1? [50 cows]

9. Use a pulley to lift the weight with G=400 N, and the pulling force F=500 N, so as to find the mechanical efficiency of the crown block.

10. The CD in the picture is an opaque baffle. Can people see object A directly?

Can you see the object A from the plane mirror MN?

1 1. Connect a light bulb directly to the power supply with the power of 100W, and connect the light bulb in series with a long conductor with the power of 8 1W, then the power lost on the conductor is: a.19wb.9wc10w.

12. An object with a volume of 5m 3 and a mass of 4.5kg; Now put it in mercury, water and kerosene. What is the buoyancy at rest? [44. 1 Niu 44. 1 Niu 39.2 Niu]

13. The resistance of the transmission line is 0.5 ohm, the transmission power is105kW, and the transmission voltage is106V. Find: [1] current of transmission line clock; [2] Electric energy consumed by heating of transmission lines; [ 100A 5000W]

14. A hollow iron ball weighs 40 Newton and has a volume of 5 decimeters 3. What is the buoyancy when put into the water?

15. Put object A on object M, and M floats on the water. If A is suspended below M and M is still floating on the water, then the volume of boiling water discharged by M is _ _ _ _ _ _ _ _.

16. If a piece of wood or iron with the same volume is thrown into the water, the wood floats on the water surface and the iron sinks to the bottom, which piece will receive greater buoyancy?

17. What is the volume of an alloy ball with a mass of 5 kg, in which the volume of lead and iron is half?

18. If something weighs 0.3 Niu, put it in a beaker filled with water, and the overflowing water weighs 0.2 Niu, then the buoyancy it receives is:

A. it may be 0.25 n.b. it may be 0.1n.c. it must be 0.3 n.d. it must be 0.2 n.

19. Put a cubic iron block with a mass of 7.8kg on a horizontal desktop with an area of 0.5m2, and work out the pressure of the iron block on the horizontal desktop. [ρ iron = 7.8× 103kg/m3]

20. At standard atmospheric pressure and 25℃, 25% of the heat released by the complete combustion of 0.2 kg of charcoal is absorbed by 5 kg of water. How much does the temperature of water increase?

2 1. A weightlifter lifts a barbell with a weight of 1600 N for 2 meters in 2 seconds, and then stays in the air for 8 seconds, so his strength in these 8 seconds is:

1600 B.0W C.400 D.320

22. As shown in the picture, the human eye can see a white pebble at B in the river at A. Now if it is from A ..

The laser beam of the laser flashlight can shine on the white pebbles, and then the laser beam is aimed at _ _ _ _ _ _ _ _ _.

_ _ _ _ _ popup. [Fill in "point B", "above point B" and "below point B"]

23. When a person goes from A to B, he advances at a constant speed at v 1 in the first half and at a constant speed at v2 in the second half. Find the average speed of this person from a to B.

24. There are two kinds of liquids, density ρ 1ρ2, each of which is m kg. Only these two liquids can be made into a mixture with a density of

)1]. ρ mixture = 2 ρ1ρ 2/[1ρ 2] 2 ρ' Married, = [1ρ 2] 2 What are the weights of the two mixed liquids? [It is known that ρ 1 > ρ 2 is mixed, and the total volume of liquid remains unchanged]