A probe sent to the surface of Mars uncovers a pure platinum disc inscribed with the message, "We'll be right back" (in Martian, of course!). The disc is 3 inches thick and 0.8 meters in diameter. The density of platinum is 21,450 kg/m^3. What is the mass of the platinum disc in pounds (lbm)?

The Martian acceleration due to gravity is 3.61 m/s^2 while Earth's gravitational constant is 32.2 ft/s^2. What is the Earth weight of the disc in Newtons?

Question

A probe sent to the surface of Mars uncovers a pure platinum disc inscribed with the message, "We'll be right back" (in Martian, of course!). The disc is 3 inches thick and 0.8 meters in diameter. The density of platinum is 21,450 kg/m^3. What is the mass of the platinum disc in pounds (lbm)? 


The Martian acceleration due to gravity is 3.61 m/s^2 while Earth's gravitational constant is 32.2 ft/s^2. What is the Earth weight of the disc in Newtons?

anonymous · Answer

the disc has got a thickness . So it is in fact a cylinder. Just find the volume of the cylinder.
V= pi*r^2 * t
t= 3 in
r = radius = 0.4 m 

Now weight is the force with which the planet will attract the body towards itself
 W=mg
where you will have calculated m by multiplying the above volume by density and g = 9.8m/s2. The force will be in newtons if you use m in kilograms and g in m/s2