90 km/h : 3.6 = 25 m/s. If you know that on earth g = 9.81 m/s^2, then all you have to do is divide the speed by g. 25/9.81 = 2.548 seconds
At least, if by 'gently rolls off a vertical cliff' means that your starting velocity equals zero.
As we know that in order to melt the copper we need to take the temperature of copper to its melting point
So here heat required to raise the temperature of copper is given as

We know that
melting temperature of copper = 1085 degree C
Specific heat capacity of copper = 385 J/kg C
now we have



now in order to melt the copper we know the heat required is

here we know that
L = 205 kJ/kg
now from above formula


now total heat required will be


As we know that

now we have

The innermost electron of an atom has the lowest level of energy while the outermost electron has the highest level of energy.
There are different energy levels in the atoms of elements, for an atom to go into an higher level it has to obtain more energy and to go to lower level it has to lose energy.<span />
Answer:
0.72 kg per cubic m
Explanation:
Mass = 14.4 kg
Volume = lbh = 4*1*5 = 20 cubic m
