Levers Questions

The long side of a crowbar (up to the turning point) has a length of 0.80 m. it is
used to pull out a nail from a board. The nail is 5 cm away from the turning point.
Calculate the force to be used if the nail can take a maximum force of 3000 N.

 A wheelbarrow weighs 20 kg when empty. A 600 N load is carried using it. The load is concentrated at a point which horizontally is 50 cm away from the wheel. The wheelbarrow, which is 2m long, has also its center of mass at this point. How much easier do we lift the load instead of carrying it on shoulders? (Take the gravity equal to 10 m/s2 if needed)

  A third class lever has a mechanical advantage

Which one of the following are correct for levers?

 I.If there is a gain in force, there is a loss in distance

II.The mechanical advantage is the ratio of the load to the force

III. In simple machines there is a gain in work

  Which diagram below shows the working principle of pliers?

A.

B.

C.