Explanation:
The power P dissipated by a heater is defined as
where V is the voltage and I is the current.
a) The current running through a 130-W heater is
b) The resistance <em>R</em><em> </em>of the heater is
where 
is our familiar Ohm's Law.
The bouyancy force is:
Since the wood-lead system is completely submerged, the bouyancy force
is FB = ĎwgVl + ĎwgVb, where Ďw is the density of water,Vl
is the volume of
the piece of lead and Vb is the volume of the wooden block. The weight of the
combined lead and wooden block is: W = ĎlgVl + ĎbgVb. Since the system is
in equilibrium, the bouyancy force must be equal to the total weight:
ĎwgVl + ĎwgVb = ĎlgVl + ĎbgVb
now we can solve for the volume of lead:
ĎwgVl â’ ĎlgVl = ĎbgVb â’ ĎwgVb
Vl(Ďw â’ Ďl) = Vb(Ďb â’ Ďw)
Vl =
Ďbâ’Ďw
Ďwâ’Ďl
Vb
Now we substitute the values for the density of lead Ďl = 11.3 Ă— 103kg/m3 ,
the density of the wood and the density of water Ďw = 1000kg/m3
. We get:
Vl =
600â’1000
1000â’11300
(0.6m Ă— 0.25m Ă— 0.08m) = 4.66 Ă— 10â’4m3
The object with a mass of 100 kg would move slower than the object with a mass of 1 kg. This is because a greater force is required to move the object with a mass of 100 kg compared to the object of 1 kg.
