For rotational equilibrium of the door we can say that torque due to weight of the door must be counter balanced by the torque of external force

here weight will act at mid point of door so its distance is half of the total distance where force is applied
here we know that

now we will have


so our applied force is 72.5 N
Answer:
I don't really know
Explanation:
I really wanted to help you, but then I realized i didnt know how to
Answer:
Option C, increases and decreases
Explanation:
When an object making noise approaches you, the wave frequency increases leading to a higher pitch. Conversely, when it moves away from you or retreats, the wave frequency decreases leading to a lower pitch. This can be observed in ambulance sirens.
C. 2000 calories.
Explanation/calculation:
Specific heat capacity = calories / mass * (final temperature - initial temperature)
1 = calories / 100 * (60 - 40)
1 = calories / 100 * 20
1 * (100 * 20) = calories
1 * 2000 = calories
2000 = calories