Explain each of the following answers:

(14) A student throws a projectile horizontally at a target a horizontal distance R away. The projectile is released from height H above the ground and strikes the target a height h below the release point, as shown above. Which of the following indicates the values that must be known for a student to calculate the initial speed of the projectile? R (A) R only (B) H only (C) H and R only (D) h and R only (E) H, h and R (15) An airplane travels horizontally at a constant velocity . An object is dropped from the plane, and one second later another object is dropped from the plane. If air resistance is negligible, what happens to the vertical distance between the two objects while they are both falling? A B (A) It increases. B) It decreases. C) It remains the same. "D) It depends on the mass of the objects. (E) It depends on the horizontal speed of the plane.(16) Two stones, represented in the figure above, are thrown from the same height with the same initial speed. Stone A is thrown vertically downward and stone B is thrown horizontally. If the stones are thrown at the same time and air resistance is negligible, which of the following is true? (A) The two stones will reach the ground at the same time with the same speed. (B) The two stones will reach the ground at the same time but with different speeds. (C) Stone will reach the ground first, but stone will have the greater speed just before hitting the ground. (D) Stone A will reach the ground first, but the two stones will have the same speed just before they hit the ground. (E) Stone will reach the ground first, and will have the greater speed just before hitting the ground.C. Projectile Launched at an angle (17) A projectile is launched from the ground with an initial velocity of 12 m/s at an angle of 30 above the horizontal. The projectile lands on a hill 7.5 m away. The height at which the projectile lands is most nearly 1.78 m (18) A projectile is launched with a speed of 40 m/s at an angle of 30" above the horizontal, as shown in the figure below. The projectile lands on a plateau 3 s later. The height Ay of the plateau is most nearly 40 m/s Ay 15 m (19) A projectile is launched with a speed of 30 m/s at an angle of 60 above the horizontal. The projectile lands on a ledge that is 15 m above the launch point, as shown. The horizontal and vertical components v. and vy , respectively, of the velocity when the projectile lands are 30 m 60 15 m Vx = 15 m/s Vy= - 19.5 m/s (20) A projectile is launched from the top of a 15 m tall building at a speed of 25 m/s at an angle of 50 above the horizontal. The horizontal distance from the base of the building to where the projectile lands is most nearly 73. 9 m(21) A spring-loaded gun can fire a projectile to a height h if it is fired straight up. If the same gun is pointed at an angle of 45 from the vertical, what maximum height can now be reached by the projectile? h (22) A cannonball is shot from the top of a 30 m high hill at a velocity of 25 m/s and at an angle of 40 above the horizontal and lands on the ground below. The speed of the cannonball at the top of its path is most nearly (A) 0 (B) 16 m/s [C) 19 m/s (D) 25 m/s (E) 29 m/s