It depends when you look at a pichture it could possibly help.
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:

Explanation:
m = Mass of object = 
mg = Weight of object = 20 N
g = Acceleration due to gravity = 
v = Final velocity = 15 m/s
u = Initial velocity = 0
d = Distance moved by the object = 150 m
= Angle of slope = 
f = Force of friction
fd = Work done against friction
The force balance of the system is

The work done against friction is
.
Average velocity = (x( 2.08 ) - x ( 0 )) / ( 2.08 s - 0 s )
x ( 2.08 ) = 1.42 * 2.08² - 0.05 * 2.08³ =
= 1.42 * 4.3264 - 0.443456 = 6.143484 - 0.443456 ≈ 5.7 m
v = ( 5.7 m - 0 m) / (2.08 s - 0 s ) = 5.7 / 2.08 m/s = 27.4 m/s
Answer:
Force = 3.333 Newton
Explanation:
Given the following data;
Change in momentum = 10 Kgm/s
Time = 3 seconds
To find the force acting on it;
In Physics, the change in momentum of a physical object is equal to the impulse experienced by the physical object.
Mathematically, it is given by the formula;
Force * time = mass * change in velocity
Impulse = force * time
Substituting into the formula, we have;
10 = force * 3
Force = 10/3
Force = 3.333 Newton