A bicycle can put out 4,400 J of work. How much work input is needed for the bicycle to reach 70% efficiency?

To determine the work input needed for the bicycle to reach 70% efficiency, we can use the formula:

Efficiency = (Work output / Work input) * 100

Given that the bicycle can put out 4,400 J of work and the desired efficiency is 70%, we can rearrange the formula to solve for the work input:

Work input = (Work output / Efficiency) * 100

Substituting the given values:

Work input = (4,400 J / 70%) * 100

To calculate this, we first need to convert the efficiency from a percentage to a decimal:

Efficiency = 70% = 0.70

Now we can substitute the values into the formula:

Work input = (4,400 J / 0.70) * 100

Simplifying the equation:

Work input = 6,285.71 J

Therefore, the work input needed for the bicycle to reach 70% efficiency is approximately 6,285.71 J.