1. A car of mass 1100 kg starts from rest at sea level and climbs a hill of alti

Question

1. A car of mass 1100 kg starts from rest at sea level and climbs a hill of altitude 50 m. At the top of the hill the car has a speed of 25 m/s. From the top of the hill the driver turns off the engine and coasts down to an altitude of 15 m. Assume the friction and the air resistance to be negligibly small. (6 points each, no partial credit, use the back of any page or any space on this page for scratch work, but these will not be graded) a) The work produced by the engine of the car is Joule. b) The speed of the car when the altitude is 15m is c) After passing the altitude of 15m, the driver climbs up again, without turning the engine on. In this case, the speed of the car would be zero at an altitude of d) In reality the friction and the air resistance are not zero. If the work needed to overcome the friction and the air resistance is 5.2x10' Joules, the answer to part (a) would change. In this case, the work prouced by the engine to climb to 50 m and have a speed of 25 m/s at the top would be Joule e) In part (d) the car reaches the top of the hill in 80 seconds. The power developed by the engine is Watts

Explanation / Answer

a)W=mgh +(1/2)m(vf^2-vi^2)

W=1100*9.8*50+(1/2)*1100(25)^2=539000+34350=573350 J

b)Using v^2=u^2+2as

At altitude 50 m

25^2=0+2a*50

a=6.25 m/sec^2

So At 15 m

v^2=0^2+2*6.25*15

v=13.7 m/sec

c)mgh+(1/2)mv^2=mgh'

9.8*h'=9.8*15+(1/2)*(13.7)^2

h'=15+9.58=24.58 m

d)Work =5.2*10^5 J+5.7*10^5 =10.9*10^5 J

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.