The mass of a person is 50kg, which rises vertically by 10m with the acceleration of the elevator a = 2m / s B man's mechanical energy increased by 5000j C lift works 6000J to human D man's kinetic energy increased by 1000 J

If the initial speed is 0, BD option is correct

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1. When the elevator is stationary, it begins to rise at a constant acceleration of A1 for 2 seconds, then decelerates at a constant acceleration of A2, and stops after 3 seconds. It is known that the elevator's rising height is 15 m. The maximum speed and the accelerations of A1 and A2 in the process of movement are calculated
2. When an object moves in a straight line with uniform speed change, the velocity is 4m / s at a certain moment, and it becomes 10m / s after 1s? Let's first specify that the initial velocity direction is positive, then the velocity of 10m / s may be positive or negative If it is positive: a = 10-4 / 1 = 6m / S ^ 2 s = (4 + 10) * 1 / 2 = 7M If it is negative: a '= - 10-4 / 1 = - 14m / S ^ 2 s' = (4-10) * 1 / 2 = 3M Then the initial velocity direction should be negative, There are four answers? I thought about it for a long time
3. When an object moves in a straight line with uniform speed change, its velocity is 4 m / s at a certain moment, and it becomes 10 m / s after 1 s. in this 1 s, the () A. The displacement may be less than 4MB. The displacement may be more than 10mc. The acceleration may be less than 4m / S2D. The acceleration may be more than 10m / S2
4. An object moves in a straight line with an acceleration of 2m / S ^ 2 and a velocity of 4m / s at a certain time. The velocity and displacement of the object in 3S are calculated
5. When an object moves in a straight line with uniform speed change, the speed is 4m / s at a certain moment; after 1s, the speed is 10m / s, then the acceleration of the object in the 1s is 0 Why do we have two situations? Sometimes we need to set the positive direction in our current problem. How can we not use it? When can we set the positive direction? When is the same as this problem? I'm in a mess. Please help me solve my problem
6. There is an object moving in a straight line with constant acceleration at an initial velocity of 0 and an acceleration of 10 meters every second, reaching 2M and 4m Then V1: V2 is equal to
7. A bus starts from a standstill and moves in a straight line with a constant acceleration of 2m every second. After 6S, it should move in a straight line with a constant speed. When it comes to the next stop, it should turn off the engine and move in a straight line with a constant speed deceleration, and then stop after 12s Finding the speed of a car at a constant speed But what about the format? What is the positive direction, the acceleration direction or the motion direction of the object
8. When the car is in emergency braking, the acceleration is 2m / s Square, and the original speed of the car is 10m / s (1) How long does it take for the car to stop after braking? (2) What is the displacement of the car from braking to stopping?
9. When the car runs at a speed of 10m / s and gets an acceleration of 2m / S2 after braking, it will be 4 s after braking
10. When the car runs at a speed of 10 meters per second and gets an acceleration of 2m / s Square after braking, what is the displacement in 4 seconds after braking?
11. A and B blocks with gravity GA = 4N and GB = 6N (a on B) are relatively stationary in the elevator with uniform deceleration, and the acceleration is 2m / s and 178; Why is the elasticity of object B just a supporting force, not a pressure The answer is support
12. When comparing the magnitude of acceleration, the sign indicates the direction, but if there is - 2m|s and#178; and - 5m|s and#178;, it is the absolute value, right
13. From - 2m / s to - 5m / s, does the acceleration increase or decrease
14. The cyclist decelerates to a slope at an initial speed of 5 m / s, the acceleration is 0.4 m / S 2, and the length of the slope is 30 m
15. The cyclist rides on a 30 m long slope at an initial speed of 5 m / S2 per second, and the acceleration is 0.4 m / S2
16. The cyclist moves in a straight line with uniform deceleration at an initial speed of 5 m / s, and the acceleration is 0.4 m / S2 (1) How long does it take to cross the distance of 30 meters? (2) What is the displacement in the second second? (3) What is the initial speed of the fifth second? (it can be solved by image)
17. If the acceleration is 0.4 m / S2 and the slope is 30 m long, the time required for the cyclist to pass the slope is 10 minutes______ s．
18. 2) The cyclist decelerates along the upward slope at an initial speed of 5 m / s. The acceleration is 0.4 m / s. how long is the distance on the slope?
19. Cyclists climb the slope at a speed of 5 m / s and do a uniform deceleration linear motion with an acceleration of 0.4 m / S ^ 2 (online, etc.) The cyclist climbs the slope at the speed of 5m / s and makes a uniform deceleration linear motion. The acceleration is 0.4m/s ^ 2. After ten seconds, how much distance does the cyclist pass on the slope
20. Someone rides a bicycle at an initial speed of 4 meters per second and drives up a slope with an acceleration of 0.2 meters per square second and a slope length of 20 meters, How long does it take for a bicycle to cross the slope?