Answer:
The force is 
Explanation:
The diagram for this question is shown on the first uploaded image
From the question we are told that
The weight of the gate is 
The vertical component of F is 
From the diagram , taking moment about the pivot we have

Where
is the weight of the gate evaluated as

=> 
=> 
=> 
From the above reaction the temperature of the surroundings will increase.
Answer:

Explanation:
The angular momentum of an object is given by:

where
m is the mass of the object
v is its velocity
r is the distance of the object from axis of rotation
Here we have:
m = 350 g = 0.35 kg is the mass of the ball
v = 9.0 m/s is the velocity
r = 3.0 m is the distance of the object from axis of rotation (if we take the ground as the centre of rotation)
Therefore, the angular momentum is:
