Chapter 4, Problem 63A

To determine

The lift force exerted by the air on the propellers.

Answer to Problem 63A

  $9000\text{N}$

Explanation of Solution

Given:

The mass of the helicopter is $m=4500\text{kg}$ and it accelerates upward at the rate of $a=2.0{\text{m/s}}^{\text{2}}$ .

Formula used:

From Newton’s second law of motion:

  $F_{net}=ma$

Where, a is the acceleration, m is the mass and $F_{net}$ is the net force.

Calculation:

The lift force exerted by the air on the propellers will be equal to the force exerted by the helicopter when it accelerates at a rate of $2.0{\text{m/s}}^{\text{2}}$ .

Then, using the Newton’s second law,

  $\begin{array}{c}\text{Lift Force = Force exerted by the helicopter}\\ =ma\\ =4500\times 2.0\\ =9000\text{N}\end{array}$

Conclusion:

Thus, the lift force exerted by the air on the propellers is 9000N.