5. A projectile of mass 0.20 kg is fired with an initial speed of 20 m/s at an angle of 60° above the horizontal. What is the kinetic energy of the projectile at its highest point? Ans. 10J 6. A ball of mass 2 kg is kicked with an initial speed of (v, 51+ 5/)m/s. What is the ratio of the potential energy, Ue (relative to ground level) to the kinetic energy, KE of the projectile at its highest point? Ans. 1 7. A 2 kg projectile moves from its initial position to a point that is displaced 20 m horizontally and 15 m above its initial position. How much work is done by the gravitational force on the projectile? Ans. - 0.29 kJ PHY102-Ch-Practice Problems-18 Page 2 8. A 4 kg particle moves from the origin to position C, having coordinates x-5 m and y-5 m as shown below. One force on the particle is the gravitational force acting in the negative y direction. Calculate the work done by the gravitational force on the particle as it goes from O to C along (a) the purple path (OAC), (b) the red path(OBC), and (e) the blue path(OC) (4) Your results should all be identical. Why? y (m) ® (5.00, 5.00) (m) O B