Question

Which has more kinetic energy: a 0.0014-kg bullet traveling at 397 m/s or a 5.9 107-kg ocean liner traveling at 13 m/s (25 knots)?

the bullet has greater kinetic energy
the ocean liner has greater kinetic energy

Justify your answer.
Ek-bullet =
J
Ek-ocean liner =
J

Answer 1

Ocean Liner because its mass is 5000 times more and the bullet's velocity squared is only 1600 times more. This means that the kinetic energy of the ocean liner will be roughly 3 times greater.

Explanation:

The kinetic energy of an object is dependent on mass and velocity.

E = ( 1 / 2 )mv²;

Energy is measured in Joules which is equal to kilogram metres squared per second squared.

1J = ( kg )( m² )( s⁻² ) or 1J = ( kg )( m² ) / ( s² )

We can substitute the mass and velocity directly into the equation because the question gives the values in metres and kilograms.

BULLET:

E = ( 1 / 2 )( 0.0014kg )( 397m / s )²;

E = ( 0.0007kg )( 157609m² )( s⁻² );

E = 110.3263kgm²s⁻²;

E = 110.3263J;

I will just skip some steps because you get the idea.

OCEAN LINER:

E = ( 1 / 2 )( 5.9107kg )( 13m / s )²;

E = 499.45415J;