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How high a hill can a car coast up (engine disengaged) if work done by friction is negligible and its initial speed is 110 km/h? (b) If, in actuality, a 750-kg car with an initial speed of 110 km/h is observed to coast up a hill to a height 22.0 m above its starting point, how much thermal energy was generated by friction? (c) What is the average force of friction if the hill has a slope 2.5º above the horizontal?

Respuesta :

Answer:

Explanation:

Initial speed v = 110 x 1000 / 60 x 60

= 30.55 m /s

If h be height achieved

1/2 m v² = mgh

v² =  2gh

h = v² / 2g

h = 30.55 x 30.55 / 2g

= 47.61 m

b ) Initial kinetic energy

= .5 x 750 x 30.55²

= 349988.43 J

Potential energy achieved at 22 m

= 750 x 9.8 x 22

= 161700 J

Heat energy generated

= loss of energy

= 349988.43  - 161700

= 188288.43 J

c ) distance covered on the slope

= h / sin 2.5

22 / .0436

= 504.58 m

average friction force x 504.58 = work done by friction

= 188288.43

average friction force = 188288.43 / 504.58

= 373.15 N

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