A.始终减小 |
B.始终增大 |
C.先减小后增大 |
D.先增大后减小 |
A.P(t1+ t2) | B.f(L1+vm t2) | C. | D.fvm(t1+ t2) |
A.50J | B.100J | C.1000J | D.2000J |
A. | B. | C. | D.0 |
A.N和对物块都不做功 |
B.N对物块做功2J,对物块不做功 |
C.N对物块不做功,对物块做功2J |
D.N和对物块所做功的代数和为0 |
A.重力对物体m做正功 |
B.合力对物体m做功为零 |
C.摩擦力对物体m做负功 |
D.支持力对物体m做正功 |
© 2017-2019 超级试练试题库,All Rights Reserved.