Answer:
The number of crates is 84580.
Explanation:
mass, m = 30 kg
height, h = 0.9 mm
Power, P = 0.5 hp = 0.5 x 746 W = 373 W
time, t = 1 minute = 60 s
Let the number of crates is n.
Power is given by the rate of doing work.

Answer:
For left = 0 N/C
For right = 0 N/C
At middle =
N/C
Explanation:
Given data :-
б =
C/ m²
Considering the two thin metal plates to be non conducting sheets of charges.
Electric field is given by

1) To the left of the plate
= 0 N/C.
2) To the right of them.
= 0 N/C.
3) Between them.
=
=
=
N/C
The branch of physics that deals with the study of force energy and motion is classic mechanics
Answer:
D) the second at the doorknob
Explanation:
The torque exerted by a force is given by:

where
F is the magnitude of the force
d is the distance between the point of application of the force and the centre of rotation
is the angle between the direction of the force and d
In this problem, we have:
- Two forces of equal magnitude F
- Both forces are perpendicular to the door, so 
- The first force is exerted at the midpoint of the door, while the 2nd force is applied at the doorknob. This means that d is the larger for the 2nd force
--> therefore, the 2nd force exerts a greater torque