Answer:
A
Explanation:
the object's mass determines the speed of the object and its kinetic energy
Let the height where we are trapped is H
now to find the time to reach the key at the bottom is given as
now we have
now if the speed of sound is considered to be 340 m/s then time taken by the sound to reach at the top is given as
now the total time is given as
now by solving above equation we have
H = 48 m
now height of one floor is 3 m
so our position must be
work is done by the pulling force which is same as the tension force in the rope. the net work done is zero for the crate since crate moves at constant velocity. but there is work done by the tension force which is equal in magnitude to the work done by the frictional force.
T = tension force in the rope = 115 N
d = displacement of the crate = 7.0 m
θ = angle between the direction of tension force and displacement = 37 deg
work done on the crate is given as
W = F d Cosθ
inserting the values given above
W = (115) (7.0) Cos37
W = 643 J
B or D, one of these are the correct answer
