y & Practice Gradebook ORION Downloadable eTextbook Assignment In the figure, a

Question

y & Practice Gradebook ORION Downloadable eTextbook Assignment In the figure, a frictionless roller coaster car of mass m-911 kg tops the first hill with speed v0-10.1 m/s at height h-37.9 m. How much work does the gravitational force do on the car from that point to (a) oint A, (b) point 8, and (c) point C? If the gravitational potential energy of the car-Earth system is taken to be zero at C, what RCES S 18) Firs hall hr2 (a) Number (b) Number (e) Number (d) Number (e) Number Units Units Units Units Units Study 5,724

Explanation / Answer

(a) Since the potential energy of the first hill and the point A is the same.

so, work done by the gravitational force from initial point to point A = 0

(b) At point B, work done on the car by the gravitational force -

= Potential energy at B - Potential energy at the initial point

= m*g*(h/2) - m*g*h = -m*g*(h/2) = -911*9.81*(37.9/2) = -169354.4 J = -169.35 kJ

(c) For point C -

Work done = Potential energy at C - Potential energy at the initial point

= 0 - m*g*h = -m*g*(h) = -911*9.81*(37.9) = -338708.8 J = -338.71 kJ

(d) Gravitational potential energy of the car-earth system at point B = m*g*(h/2)

= 911*9.81*(37.9/2)

= 169354.4 J = 169.35 kJ

(e) Gravitational potential energy of the car-earth system at point A = m*g*(h)

= 911*9.81*(37.9)

= 338708.8 J = 338.71 kJ

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