Consider a father pushing a child on a playground merry-go-round. the system has a moment of inertia of 84.4 kg · m2. the father exerts a force on the merry-go-round perpendicular to its 1.50 m radius to achieve a torque of 375 n · m.(a) calculate the rotational kinetic energy (in j) in the merry-go-round plus child when they have an angular velocity of 29.2 rpm. j(b) using energy considerations, find the number of revolutions the father will have to push to achieve this angular velocity starting from rest. revolutions(c) again, using energy considerations, calculate the force (in n) the father must exert to stop the merry-go-round in seven revolutions. n

A)The rotational kinetic energy is ≈ 9.9962 J

B)The number of revolutions to achieve that angular velocity = 0.0085

C)Force to stop it = 0.15152N

Explanation:

Given :

A)

Rotational kinetic energy :

where,

⇒

⇒

Thus the energy is ≈ 9.9962 J

B) Work done by the torque = The change in rotational kinetic energy

where ,

Thus,

The number of revolutions = 0.0085

C)

7 revolutions :

Force = 0.15152N

we need answer choices

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.