Work is（ ）when energy is removed from the system.
A: positive
B: negative
C: down
D: Not sure
A: positive
B: negative
C: down
D: Not sure
举一反三
- Work is taken negative when the work is done by the system and heat is taken as positive when it is transferred into the system. （ ）
- The delayed value of rotation angle of the output shaft when the rotation of input shaft turns from positive to negative is . A:
- The work done by static friction can be: A: Positive B: Negative C: Zero D: Any of the others
- When a system moves from A state along path I to B state, it releases heat of 100 J and obtains 50 J work at the same time; when the system does 80J work from A state along path Ⅱ to B state, then Q is（ ） A: 70J B: 30J C: －30J D: －70J
- Reactions to the online management system were more positive ______ those to a paper-based version of the same system.