Kinematics Question 352
Question: A car moves with a speed of 60 km/hr from point A to point B and then with the speed of 40 km/hr from point B to point C. Further it moves to a point D with a speed equal to it’s average speed between A and C. Points A, B, C and D are collinear and equid it’stant. The average speed of the car between A and D it’s
Options:
A) $ 30km/hr $
B) $ 50km/hr $
C) $ \text{48 }km/hr $
D) $ \text{60 }km/hr $
Show Answer
Answer:
Correct Answer: C
Solution:
Let the points A, B, C and D be separated by 1 km. Then $ t _{AB}=\frac{1}{60}hr,t _{BC}=\frac{1}{40}hr $
$ \therefore <v _{AC}>=\frac{1+1}{\frac{1}{60}+\frac{1}{40}}=48km/hr\Rightarrow t _{CD}\frac{1}{48}hr $
$ Now<v _{AD}>=\frac{1+1+1}{\frac{1}{60}+\frac{1}{40}+\frac{1}{48}}=48km/hr $
