PartA: Ryan, needs to get to his physics class to take his final exam. He is on

Question

PartA: Ryan, needs to get to his physics class to take his final exam. He is on a cliff, which is about 17 meters above the building. He starts to ride his skateboard at a speed of 7m/s. What is Ryans speed when he reaches the building? Assume that the building is ground level and that Ryan%u2019s mass is 68.43kg.

Part B: Ryan, nervous for his physics exam, does not pay attention to anything that%u2019s in front of him. In fact, coming closer and closer to Ryan is another student riding their skateboard at the same direction Ryan is going. When Ryan finally realizes this, he is going at a speed of 20m/s. the student in front of Ryan is initially going 12m/s. If the student in front of Ryan has a mass of 83.0kg, what is the final speed of the student that Ryan collides to? Assume that after the collision Ryan stops moving completely. (Vf=0)

Part C: After taking his physics exam, Ryan leaves class and begins to ride his skateboard towards his car. He begins to ride with an initial velocity of 22m/s. It just so happens that ahead of him is his physics professor riding his roller skates toward the same direction Ryan is going. His professor is going at a speed of 14m/s and has a mass of 98kg. Ryan, depressed over how his day is going, does not pay attention to the fact that his professor is right ahead of him and collides with him. The two of them hold on to on another as they both go toward the same direction but with a new speed. What is their speed?

Explanation / Answer

Part A)

using conservation of energy: 1/2 * m* v^2-1/2 * m*u^2= m*g*h     using g= 9.8   

m=68.3 and u=7

gives v= 19.55 m/s

part B) using conervation of momnetum

m1*u1 + m2*u2 = m1*v1+ m2*v2

68.43*20+83*12= 0+83*v2

gives v2=28.49 m/s

part C) using conervation of momnetum

m1*u1 + m2*u2 = (m1+ m2)v

68.43*22+98*14=(68.43+98)*v

gives V=17.29 m/s

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