Question

select the correct answer
richard wrote a list of the advantages of using any one of the six simple machines. his list is below. which statement about simple machines is not correct?
a. some simple machines produce an output force greater than the input force
b. some simple machines produce an output force in a different direction than the input force
c. some simple machines have a work - output greater than the work - input
d. some simple machines increase the distance through which a force is applied

Explanation:

Simple machines遵循能量守恒定律，其输出功（work output）不可能大于输入功（work input）。理想机械的输出功等于输入功，实际机械因摩擦等因素输出功小于输入功，故C项错误。A项（如杠杆可增力）、B项（如定滑轮改变力的方向）、D项（如为省力增大施力距离）均正确。

Answer:

C. Some simple machines have a work output greater than the work input