A 9.90-g bullet has a speed of 1.33 km/s.
(a) What is its kinetic energy in joules?
(b) What is the bullet's kinetic energy if its speed is halved?
(c) What is the bullet's kinetic energy if its speed is doubled?
K = 1/2 mv2
plug in your numbers for m and v to get K.
Since K varies as v2, if the speed changes by a factor of 2, the energy changes by a factor of 22=4