I think it is equal for your question
Kinetic energy = 0.5 * m * v²
m mass
v velocity
If the velocity stays the same and the kinetic energy goes down by a factor of 2, the mass must go down by a factor of 2 also.
IF the toss was straight upward, then the kinetic energy it got
from the toss is the gravitational potential energy it has at the top,
where it stops rising and starts falling.
Potential energy = (mass) x (gravity) x (height)
= (0.15 kg) x (9.8 m/s²) x (20 m)
= 29.4 kg-m²/s² = 29.4 joules .
