Concepts Of Physics MCQ Edition [Volume 1]PhysicsCircular Motion
A simple pendulum with a bob of mass m hangs from the ceiling of a car involved in a stunt film shoot. The car travels upward along an inclined cliff at a speed v , leaps off the cliff, and lands some distance away. Suppose R is the maximum height reached by the car above the cliff's top. The tension in the string while the car is airborne is
Options
- Azero
- Bmg + mv^2 R
- Cmg - mv^2 R
- Dmg
Correct answer
A. zero
Step-by-step solution
When the car is airborne, it is in a state of free fall and its acceleration is equal to the acceleration due to gravity g directed downwards. In the non-inertial frame of reference of the car, a pseudo force of magnitude mg acts on the pendulum bob in the upward direction. The true gravitational force acting on the bob is mg in the downward direction. The pseudo force exactly cancels the gravitational force, making the effective acceleration due to gravity zero in the car's frame. Since the effective gravity is ze