Answer:
it cannot be considered a physical change because it occur from the chemical reaction.
Explanation:
because physical change is the change of the size,volume, density,flexibility. in other words its a change in the outer appearance or change in which we can see or feel without using a tool or a machine
hope it help just my opinion
Answer:
L = 1.545 m
Explanation:
Let the total length of the rod is L
now the torque must applied on the other end of the rod so that it will balance the torque due to weight of rock on other side of fulcrum
so we will have

so we have

F = 663 N


Answer:
Work done in both the cases will be same
Explanation:
As we know that the work done against gravity is given as

here we know that gravitational force is a conservative force and the work done against gravitational force is independent of the path
So here the work done by person to move the object between two different heights will be independent of the path they choose
So for the first person and second person will be same in both the cases because the height through which the boxes are transferred will be same in both the cases
Answer:
V(t1-t0)
Explanation:
Moving 'uniformly' means constant velocity (speed). the formula for constant speed motion is
=( change in position/ change in time)
where,
V is speed
given in the statement :
change in time = t = t1-t0
let the constant speed be ' V '
disance = X = X1-X0
applying the above mentioned formula: V = 
V = X/t
X = Vt
the distance X1-X0 = Vt =V(t1-t0)
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