(20 14? As shown in Figure A, the second model of Minhang District is a simple model of pile driver. An object with mass m= 1kg moves from the contact with the nail under the action of tensile force F. A, the mechanical energy of an object rising at the height of 1m is e = mgh1+12mv12, that is,10×1+12×/kloc-. The maximum velocity of an object during its ascent is obtained as follows: v1= 2m/s; According to the velocity displacement formula of uniform linear motion, the following results are obtained: v12 = 2ah1; It is known that the acceleration of an object during its ascent is: a = v122h1= 42×1=.

C. According to the velocity displacement formula: V22 = 2ah', the solution is V2 = 2ah' = 2× 2× 0.25m/s =1m/s;

According to Newton's second law: F-mg=ma,

Solution: f = mg+ma =/kloc-0 /×12n =12n,

Then the instantaneous power of the pulling force F is: p = Fv =12×1w =12w. So, C is correct.

D, according to the conservation of mechanical energy, the kinetic energy of the contact between the object and the nail is 12J, according to the conservation of energy:

mgh2+ 12mv2=fh2，

Alternative data: = 6 10n. Therefore, d is correct.

Therefore: alkaline catalytic decomposition ..