5. A 1200kg car drives up a 20m hill, starting at 8 m/s and reaching the top at

Question

5. A 1200kg car drives up a 20m hill, starting at 8 m/s and reaching the top at 10 m/s. (a) How much work was done by gravity during this trip? (b) Assuming no air resistance, how much work was done by the car's engine? Initial Final ty 6. In the above figure is an Atwood machine: a machine composed of two blocks, one of mass m 250g and one of mass m2 100g, a massless rope and a massless pulley. If the two masses are released from rest as shown in the figure, at what speed does mi hit the ground after falling some h 12cm?

Explanation / Answer

5) work done by gravity = mgh

= 1200*9.8*20 = 235200 J

b) work done by the car's engine = 0.5m(v2^2 - v1^2)

= 0.5*1200*(10^2 - 8^2)

= 21600 J

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