To project a body of mass $m$ from earth's surface to infinity, the required kinetic energy is (assume, the radius of earth is $R_E, g=$ acceleration due to gravity on the surface of earth):

<p>The kinetic energy required to project a body of mass $m$ from the Earth's surface to infinity, also known as the escape kinetic energy, can be calculated using the concept of gravitational potential energy. The escape velocity $v_e$ is the velocity a body must have to escape the gravitational field of the Earth without any further propulsion. The formula for escape velocity is:</p> <p>$v_e = \sqrt{2gR_E}$</p> <p>Where $g$ is the acceleration due to gravity on the surface of Earth and $R_E$ is the radius of the Earth. The kinetic energy $K$ required for this is given by:</p> <p>$K = \frac{1}{2}mv_e^2$</p> <p>Substituting the escape velocity formula into the kinetic energy formula gives:</p> <p>$K = \frac{1}{2}m\left(2gR_E\right)$</p> <p>$K = \frac{1}{2} \times 2 \times mgR_E$</p> <p>$K = mgR_E$</p> <p>Therefore, the required kinetic energy to project a body of mass $m$ from Earth's surface to infinity is $mgR_E$. So, the correct answer is:</p> <p>Option C: $mgR_E$</p>