A human "cannon ball" in the circus is shot at a speed of 21.0 m/s at an angle of 20above the horizontal from a platform that is 15.0 m above the ground.

i) If the acrobat has a mass of 56.0 kg, what is his gravitational potential energy relative to the ground when he is at the highest point of his flight? Ignore the effects of air resistance. [9.69 x 103J]

ii) If the net in which he lands is 2.00 m above the ground, how fast is he travelling when he hits it? [26.4 m/s]

9) A model rocket has a mass of 3.00 kg. It is fired so that when it is 220 m above the ground it is travelling vertically upward at 165 m/s. At that point its fuel runs out so that the rest of its flight is without power. Assume that the effect of air friction is negligible and that all potential energies are measured from the ground.

i) What is the mechanical energy of the rocket, relative to the ground, when it is 220 m above the ground? [4.73 x 104J]

ii) When it reaches the highest point on its trajectory, what will its gravitational potential energy be? [4.73 x 104J]

iii) How far above the ground is the rocket at its highest point? [1.61 x 103m]

iv) When it hits the ground, what is its speed? [178 m/s]