Question

a particle moving along a straight line with uniform acceleration has velocities 7 m/s at P and 17 m/s at Q. If R is the mid point of PQ. Then : a) the average velocity between R and Q is 15 m/s. b) the ratio of time to go from P to R and that from R to Q is 3:2. c) the velocity at R is 10 m/s. d) the average velocity between P and R is 10 m/s.q

Answer 1

The correct answer is option (b) The ratio of time to go from P to R and heat from R to Q is 3;2.

We know that v² - u² = 2as

17² - 7² = 2a * 2x

240 = 4ax

ax = 60

Now v'² - u² = 2ax

v'²  = u² + 2ax

     = 7² + 2ax

     = 49 + 2 * 60

     =  169

v' = 13 m/s

Now, v' = u + at1

or, 13 = 7 + at1

at1 = 6

Similarly, at2 = 17-13 = 4

Now, at1/at2 = 6/4

or, t1/t2 = 3/2 Answer.