An IGCSE student thinks it may be possible to identify different rocks (A, B and C) by measuring their densities. She uses an electronic balance to measure the mass of each sample and uses the displacement
method to determine the volume of each sample.

See the answer below

Explanation:

a. The volume in the first measuring cylinder reads 70 while that of the second reads 95  . Hence;

V1 = 70  

V2 = 95  

b. An object will always displace its own volume in a liquid. Hence:

Volume V of the rock sample = V2 - V1

   = 95 - 70 = 25  

c. Mass of A = 102 g

   Volume of A = 25  

Density = mass/volume

Hence, density of A = 102/25 = 4.08 g/

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it