Question

A block and tackle system consisting of 5 pulleys is used to raise a load of 400N through a height of 10m . If the work done agaist friction is 100J, calculate the work done by the effort

Answer 1

To calculate the work done by the effort in a block and tackle system, we can apply the principle that the work done is equal to the work done against gravity plus the work done against friction.

**Step 1: Calculate the work done against gravity.**

The load is 400 N and it is raised through a height of 10 m. The work done against gravity (W_gravity) can be calculated using the formula:

\[
W_{\text{gravity}} = \text{Force} \times \text{Distance} = 400 \, \text{N} \times 10 \, \text{m} = 4000 \, \text{J}
\]

**Step 2: Calculate the total work done against friction.**

The work done against friction is given as 100 J.

**Step 3: Calculate the total work done by the effort.**

The total work done by the effort (W_effort) is the sum of the work done against gravity and the work done against friction:

\[
W_{\text{effort}} = W_{\text{gravity}} + W_{\text{friction}}
\]

\[
W_{\text{effort}} = 4000 \, \text{J} + 100 \, \text{J} = 4100 \, \text{J}
\]

**Final Result:**

The work done by the effort is \( \boxed{4100 \, \text{J}} \).