6. A 2 kg ball is thrown horizontally from a height of 5 m. It hits the ground with a speed of 12 m/s. With what speed was it thrown? Find the speed of a rock which is thrown off the top of a 20 m tall building at 15 m/s when it makes contact with a bird which is flying at an altitude of 10 m above the ground. 8. A5 kg block is compressed 20 cm onto a horizontal spring with constant 200 N/m. When released, it flies off the platform and lands on the ground with a speed of 6.39 m/s. How high above the ground is the platform? 9. At Point A, a pendulum bob with mass 5 kg has 15 J of gravitational potential energy relative to point B and is released from rest. Point A Point C a. What is its kinetic energy at point B? Point B What is its speed at point B? What is its height relative to point B? hp