Answer:
(A) 2.4 N-m
(B) 
(C) 315.426 rad/sec
(D) 1741.13 J
(E) 725.481 rad
Explanation:
We have given mass of the disk m = 4.9 kg
Radius r = 0.12 m, that is distance = 0.12 m
Force F = 20 N
(a) Torque is equal to product of force and distance
So torque
, here F is force and r is distance
So 
(B) Moment of inertia is equal to 
So 
Torque is equal to 
So angular acceleration 
(C) As the disk starts from rest
So initial angular speed 
Time t = 4.6 sec
From first equation of motion we know that 
So 
(D) Kinetic energy is equal to 
(E) From second equation of motion

Answer:
Therefore, the temperature at which the Fahrenheit scale reading is equal to half of the Celsius scale is −24.6∘C .
mass of the box = 20 kg
force of friction on the box due to surface



similarly kinetic friction on it



now the weight of the suspended block will be

so here the weight of the suspended block is less than the limiting friction on it
So here we will say that friction will counter balance the weight of the suspended block and it will not move at all
So acceleration of the box will be zero
At the position of terminal speed the net acceleration of the ball will become zero
As we know that terminal speed will always reach when net force on the ball is zero and its speed will become constant.
So here at this position we can say



now when ball is moving at half of the terminal speed in upward direction then net force on the ball in downwards direction will be


here speed of the ball is half of the terminal speed

then we have


now acceleration will be given as

now we have

downwards