Question

-. A machine cannot be 100% efficient.
2. A pulley has a groove cut along its rim.
. A second class lever always increases the
effect of effort applied.
. Mechanical advantage of a third class lever
is always less than one.
. It takes less effort to insert a screw into
wood than to insert a nail.​

Answer 1

Answer:

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Answer 2

Answer:

1 ) A Machine cannot be 100% efficient because output of machine is always less than input.

2) A pulley has a groove cut along its rim because the groove prevents the rope from slipping of the disc.

i also use the same physics book