There is a bell at the top of a tower they is 45 m high. the bell weighs 60kg. the bell has —— energy. calculate it

Any object that's at the "top of a tower" has gravitational potential energy.

The bell does not "weigh" 60 kg.  

"kg" is an abbreviation for "kilogram" ... a unit of mass, not weight or force.

I'll assume that "60 kg" is the mass of the bell, and now I'll go ahead and solve the problem that I just invented:

The gravitational potential energy of any object is

PE = (gravity acceleration)·(object's mass)·(height above somewhere)

-- The acceleration of gravity on Earth is 9.8 m/s²

-- The object's mass is 60 kg

-- Use the "height" above the ground, just like the height of the tower.

PE = (9.8 m/s²)·(60 kg)·(45m)

PE = 26,460 Joules

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explanation:

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg