ANSWER
a. reducing the velocity of the object by half
EXPLANATION
The kinetic energy of an object of mass m moving at a velocity v is,
[tex]KE=\frac{1}{2}mv^2[/tex]As we can see, the kinetic energy of an object is directly proportional to the object's mass and to the square of the object's velocity.
If the mass of the object is halved, then the kinetic energy of the object will be halved,
[tex]KE_2=\frac{1}{2}\frac{m}{2}v^2=\frac{KE_1}{2}[/tex]If the velocity of the object is halved instead, then the kinetic energy will be reduced by 4,
[tex]KE_2=\frac{1}{2}m\left(\frac{v}{2}\right)^2=\frac{1}{2}m\frac{v^2}{4}=\frac{KE_1}{4}[/tex]Hence, the option that will cause the greatest decrease in an object's kinetic energy is reducing the velocity of the object by half.
