Mechanical Engineering - Machine Design - Discussion

A lever is a simple machine that makes work easier for use; it involves moving a load around a pivot using a force. Many of our basic tools use levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and tongs (2 class 3 levers).

In a Type 1 Lever, the pivot (fulcrum) is between the effort and the load. In an off-center type one lever (like a pliers), the load is larger than the effort, but is moved through a smaller distance.

In a Type 2 Lever, the load is between the pivot (fulcrum) and the effort.

In a Type 3 Lever, the effort is between the pivot (fulcrum) and the load.

There are two types of tongs one comes under type 1 and other one comes under type 3. If load is applied in between fulcrum and resistance then that type of tong is type 3 tong and if fulcrum is in between effort and resistance then it is of type 1 (scissors is the similer example of type 1 tong).

Answer is Tong because if you take sugar tong the effort is applied at middle of load and fulcrum.

Whereas in loaded safety valve the applied at one end of the lever which is next to the load (Loaded with spring) and another end is pivoted. So safety valve comes under 2nd type lever.

A pair of tongs comes under the first type, because fulcrum is at middle, load and efforts are either end. Depending upon its design its mechanical advantage varies from <1 to >1.

The 3rd class lever means pivot at the end, load at other end and effort is in the middle. For example, our human arm. Bicep is effort palm is where you take the load.

If it is sugar tongs the answer given above is correct.

For welding tongs it would be Type 1.

Pair of tongs is of first type lever in which fulcrum is between load and effort.

Answer is C (in safety valve effort is at mid of load and hinge).

Pair of tongs comes under 1st class of levers.

Pictures can make clear understanding.