# Question 1. Use a diagram to describe what fricti…

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Question 1. Use a diagram to describe what friction is and why it exists. What two things do not contribute to friction (i.e. what is friction not dependent upon)? Give three examples of where friction is important in everyday life. Question 2. Stranded on a tropical island, Melissa loads her slingshot and fires a compact seashell at a coconut. The seashell leaves the slingshot at ground level at a velocity of 24m/s making an angle of 53° with the horizontal. The coconut is hit at the top of the shell’s trajectory. Ignoring air resistance: a. What is the velocity with which the seashell hits the coconut? b. How high is the coconut? Question 3. You are standing perfectly still and then you take a step forward. Before the step your momentum was zero, but afterward you have some momentum. Is the principle of conservation of momentum violated in this case? Explain your reasoning. Question 4. A 65kg boy and his 40kg sister, both wearing roller blades face each other at rest. The girl pushes the boy hard, sending him backwards with a velocity of 2.9ms-1 towards the west. Ignore friction. a. Describe the subsequent motion of the girl b. How much chemical energy is converted into mechanical energy in the girl’s muscles? c. Is the momentum of the boy-girl system conserved in the pushing apart process? Question 5. A pole vaulter falls from a height of 6m onto a foam rubber pad. Can you calculate the speed immediately before they reach the pad? Can you calculate the force exerted on them by the pad? Explain and calculate these if possible. Question 6. A canon ball is fired from a canon upwards at an angle above the horizontal. a. Sketch a graph showing the height of this canon ball over time if it was fired at 30°, 45° and 60° above the horizontal. b. Sketch showing the acceleration of the canon ball over time if it was fired at 30°, 45° and 60° above the horizontal. c. At what point in the flight of the canon ball is the velocity at a minimum? . . Question 7. A 1300kg car travels north along Murdoch Drive at 65km/h. The car collides and becomes stuck to a 5000kg truck travelling west at along South Street at the intersection of South Street and Murdoch Drive. What is the final velocity of the vehicles after the collision if the truck was travelling at 70km/h? Include a diagram Question 8. A 400g lemming (does anyone remember that old computer game?) waddles horizontally off a small 4.9m high cliff with a speed of 0.5ms-1.How far from the base of the cliff will the lemming land? What will be the lemming’s speed upon landing?