Question

Blu ray IS disc spins at 7200 revlmin, what is the radial acceleration of a point on the outer rim of the dish? the disc is 12cm in diameter.​

Answer 1

Answer:

Since the bolt gets detached while the rocket is moving, it would have some initial velocity due to inertia. Hence the bolt would travel some height after which it reaches zero velocity. At this point it starts falling towards the ground under free fall.

The values required for calculation are:

Initial Velocity (u) = Speed of Rocket = 10 m/s

Final Velocity (v) = 0 m/s (At the highest point)

Acceleration = - 10 m/s² (Since g acts downwards)

Now let's first calculate the distance travelled by the bolt after getting detached. Using the third equation of motion we get:

⇒ v² - u² = 2as

⇒ 0² - 10² = 2 (-10) s

(a = -10, since the gravity is acting downwards while the object is moving upwards.)

⇒ -100 = -20 s

⇒ s = 100/20 = 5 m

Hence the bolt has travelled 5 m from the initial point where it gets detached. Hence the bolt starts falling with zero initial velocity at 125 m.

At this point, the values are:

Initial Velocity (u) = 0 m/s

Height from ground (s) = 125 m

Acceleration = + 10 m/s²

Now using third equation of motion again we get:

⇒ v² - 0² = 2 (10) (125)

⇒ v² = 2500

⇒ v = √2500

⇒ v = 50 m/s

Hence the bolt would strike the ground with a speed of 50 m/s.