Answer: a) Case 2 b) Case 1
Explanation:
a) By definition, the magnitude of a torque, referred to a given point, is expressed as the product of the force that causes the torque, times the perpendicular distance to the reference point.
If we assume that the only force acting on the arm is the weight of the arm, and that this is concentrated in a point in the center of it (taking the arm as a solid bar with the center of mass at the mid-point), clearly the torque will be the greatest when the force be exactly perpendicular, which is the case of the arm placed straight out parallel to the ground (Case 2).
b) As the torque and the angular acceleration are directly proportional each other (being the rotational inertia the proportionality constant) the angular acceleration will be maximum when torque be maximum also, which is the case that the arm begins to swim, due to the perpendicular distance to the shoulder is the maximum possible (Case 1).
Rock dug out from the deep inside earth and refined.
Explanation:
Ores are usually rocks dug out from deep within the earth and refined.
An ore is an aggregate of metalliferous minerals with gangue that can be won at profit under current economic conditions.
Ores are rocks and rocks can be ores if they contain viable economic minerals.
They are usually naturally formed and they contain different minerals.
For example cassiterite is a known ore of tin.
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Answer:
He sowed the seeds
Explanation:
While the question should have given the person who did the sowing for example the seeds were sown by him/ her/ the farmer/ or any name. Therefore, voice is given in passive and to change passive voice to active voice then the sentence will read as follows assuming that the seeds were sown by him
He sowed the seeds
Answer:
No
Explanation:
The force of tension exerted by the string on the rock acts as centripetal force, so its direction is always towards the centre of the circle.
However, the direction of motion of the rock is always tangential to the circle: this means that the force is always perpendicular to the direction of motion of the rock.
As we know, the work done by a force on an object is
where
F is the magnitude of the force
d is the displacement of the object
is the angle between the force and the displacement
In this situation, F and d are perpendicular, so 
, therefore 
and the work done is zero:
