![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
The mass of the inclined trolley is m and the height is h. When an object with mass m slides down from the top of the trolley, the speed of the object sliding away from the bottom of the inclined trolley is set as V, regardless of all friction. The following statements are: ① the speed of the object sliding away from the trolley v = 2GH; ② the speed of the object sliding away from the trolley V < 2GH; ③ the speed of the object sliding away from the trolley v = MVM; ④ the speed of the object sliding away from the trolley V < MV M where the correct one is () A. Only (1) and (3) correct B. only (1) and (4) correct C. only (2) and (3) correct D. only (2) and (4) correct
According to the momentum conservation of the object and the car in the horizontal direction, if the right orientation is positive, we can get 0 = mv level - MV, so v = mv level M, because V level < V, so the speed of the car when the block slides away from the car is V < MVM, so ④ is correct; when the car is not moving, according to the conservation of mechanical energy, we can get MGH = 12mv2, so v = 2GH, because of the motion of the car, according to the conservation of energy, we can know that the speed of the block is V < MVM, so ④ is correct The speed of the block sliding away from the car is less than 2GH, so ② is correct
On the knowledge of physical momentum
Put a piece of white paper under a piece of wood, quickly pull hard, the block almost does not move, but slowly force is not like this! Why? Use momentum knowledge to answer!
The friction force acts on the wood block, f * t = MV (momentum change), which is quite right
If you pull slowly, the action accumulates and changes the state of the block
Throw an object with a mass of 1kg at the speed V level, and after throwing the object to the ground, what is its momentum change in 3 seconds before landing
That's all!
Because an object is only affected by gravity, the change of momentum is the change of impulse
Δ P = ft = Mgt = 1 * 10 * 3 = 30kg. M / s, vertically downward
RELATED INFORMATIONS
- 1. 1. An object is thrown up 420 away from the ground and lands after 10 seconds, 2. The car with mass m moves forward on a smooth horizontal plane with speed V1. There is a man with mass m on it. He asks how fast the car is when the man jumps backward and horizontally from the speed V2 of the car, This involves the relative speed, I think people's speed should be (V1 - V2) But the answer is (v-v2). He sets V to make the speed of the car after jumping. I think the speed can't change suddenly. It should be v1. Why
- 2. An object of mass m collides with a stationary object of mass m at its initial velocity v. after the collision, the momentum of the two objects is equal. The possibility of M / M is obtained
- 3. The mass m moves at the velocity V and collides with the mass M. after the collision, the momentum of the mass m is equal to that of the mass M. the mass ratio m m m may be () A. 2B. 3C. 4D. 5
- 4. When will high school physics consider using the kinetic energy theorem, the conservation of mechanical energy, the conservation of energy, the conservation of momentum theorem, and the conservation of momentum theorem? And the left hand rule, how to use the right hand rule? And how to use Lenz's law?
- 5. At the initial velocity of V0 = 10m / s, throw a small ball with mass of M = 2kg at an angle of 30 degrees with the horizontal direction, ignoring the effect of air resistance. G is taken as 10m / S ^ 2. Calculate the velocity of the small ball at the end of the second after throwing
- 6. How to judge a problem is to use kinetic energy theorem, momentum theorem, energy conservation or energy conservation. What is the ideological basis? How to correctly analyze the problem? How to correct the formula for the problem that can't be solved
- 7. Conservation of momentum, conservation of energy A smooth inclined plane with height h and angle a is placed on a smooth horizontal plane, and a slider slides along the inclined plane to the bottom. If the velocity of the inclined plane is V2, the velocity of the slider relative to the inclined plane is V1, Simultaneous: MGH = 1 / 2m (v1sina) ^ 2 + 1 / 2mv2 ^ 2 + 1 / 2m (v1cosa-v2) ^ 2 mv1cosa=(M+m)v2
- 8. There is a formula for the conservation of momentum: how can p = √ 2mek be deduced, and under what conditions can it be used?
- 9. A ball with mass m and velocity V collides with a static B ball with mass 3M. The collision may be elastic or inelastic, so the velocity of B ball may be () A. 0.6vB. 0.4vC. 0.2vD. 0.1v
- 10. Derivation process of stiffness coefficient relationship of series spring? Series connection: stiffness coefficient relation 1 / k = 1 / K1 + 1 / K2 How to deduce? The detailed process is needed If you can, add the parallel derivation process. But the best answer is to look at the series
- 11. Momentum: when m and V are constant, only the direction of V changes, then the momentum changes
- 12. The kinetic energy of electron is equal to the static energy. What's the wavelength?
- 13. As shown in the figure, the length of the uniform thin straight bar AB is l, the mass is m, and the instantaneous velocity of point a is V, then the momentum of the bar AB is? What about kinetic energy?
- 14. If two objects have the same momentum, they must have () A. the same velocity B. the same mass C. the same direction of motion If two objects have the same momentum, they must have () A. Same speed B. same mass C. Same direction of motion D. same acceleration
- 15. In the following motion processes, in any equal time, the momentum change of the object is always equal () A. Uniform circular motion B. free falling motion C. horizontal throwing motion D. uniform deceleration linear motion
- 16. Changing the known formula P = M1 · V1 + M2 · V2 / M1 + M2 into the known formula of P, m, V1, V2, M2 (P ≠ V2)
- 17. How to deduce the centripetal acceleration formula a = R ω ^ 2?
- 18. The physical formulas of the second half of the semester are the theorem of kinetic energy, the law of conservation of momentum and so on,
- 19. The derivation process of physical Acceleration Formula in grade one of senior high school needs formula and derivation process urgently!
- 20. Detailed derivation of Acceleration Formula by difference method in senior one physics