Question:

The rotor�s velocity of a helicopter engine changes from $ 330 \,rev/min $ to $ 110 \,rev/min $ in 2 minutes. How long does the rotor blades take to stop?

Updated On: Aug 20, 2024
  • $ 3 \,min $
  • $ 4 \,min $
  • $ 5 \,min $
  • $ 6 \,min $
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The Correct Option is A

Solution and Explanation

Acceleration of helicopter blades $\alpha = \frac{\omega_2 - \omega_1}{t}$ $\alpha = \frac{330-110}{2}$ $ = 110\,rev/min^2$ Final angular velocity of blades will be zero i. e., $\omega = 0$ From equation of rotational motion $\omega = \omega - \alpha t$ $0 = 330 -110 \times t$ $t = 3 \,min$
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Concepts Used:

Motion in a straight line

The motion in a straight line is an object changes its position with respect to its surroundings with time, then it is called in motion. It is a change in the position of an object over time. It is nothing but linear motion. 

Types of Linear Motion:

Linear motion is also known as the Rectilinear Motion which are of two types:

  1. Uniform linear motion with constant velocity or zero acceleration: If a body travels in a straight line by covering an equal amount of distance in an equal interval of time then it is said to have uniform motion.
  2. Non-Uniform linear motion with variable velocity or non-zero acceleration: Not like the uniform acceleration, the body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. The rate of change of its velocity changes at different points of time during its movement.