Identify the arrows that show input force

Figure 1: Downward arrow

Figure 2: Downward arrow

Figure 3: Upward arrow on the rod.

Explanation:

The initial force which is applied for a machine to begin work is known as an input force. Machines are designed such that input force increases so that output force increases. Mechanical advantage determines the quality of machine. It is the ratio of output force to the input force.

In figure 1, input force is applied in downward direction so the lever lifts up the barrel at the other end.

In figure 2, input force is applied downwards so that rope is pulled down and at the other end, the load is lifted upwards.

In figure 3, Input force lifts is applied in upward direction to lift the rod which drives the wheel.