Answer:a
Explanation:
We have to lift the load two loads up one story, so energy required is
let m be the mass of each load and h is the height of each story
Energy 

Here energy gained is the potential energy which depends upon the datum(floor).
For lifting one load up one story
Energy required

thus
is half of 
So option a is correct
Note that this is a position vs time graph.
From A to B, the graph is a straight line with a nonzero slope. This indicates a constant velocity.
From B to C, the graph is a straight line with 0 slope. This indicates a constant position, i.e. the object remains stationary.
From C to D, the graph is a straight line with a nonzero slope. This indicates a constant velocity.
Yeah, because of it's short frequencies, ultraviolet rays can travel through empty space- D
: D
Answer:
•→ The motion of a particle or body in S.H.M acts towards a fixed point.
•→ Acceleration of the body under S.H.M is proportional to its displacement.
•→ This motion is periodic.
•→ Mechanical energy is conserved in S.H.M
Explanation:
S.H.M is Simple Harmonic Motion

Answer:
it may be because of the movement of the atoms. i believe that the heat of the warm water makes it move faster, thus making the object float due to upthrust, or air pressure