Question

plsss some one answer!!
A car moves with uniform acceleration along a straight line PQR. Its speed at P and R are 5 m/s and
25 m/s respectively. If PO: OR=1:2; the ratio of the times taken by car to travel distance PO and
QR is:
A) 1:2
B) 2:1
C)1:3
D) 1:1​

Answer 1

Answer:

Option (D) 1 : 1

Explanation:

Initial speed of the car at P

$u=5$ m/s

Speed of the car at R (Final speed)

$v=25 m/s$

If the common ratio is x then

Distance $PQ=x$

Distance $QR=2x$

Therefore, total distance

$s=x+2x=3x$

Let the constant acceleration be a

From the third equation of motion

$v^2=u^2+2as$

$25^2=5^2+2a\times 3x$

$\implies ax=100$

If the velocity at Q is v' then

$v'^2=u^2+2a(x)$

$\implies v'^2=5^2+2\times 100$

$\implies v'^2=25+200$

$\implies v'=225$

$\implies v'=15$ m/s

If time taken in travelling from P to R is T then

From the first equation of motion

$v=u+aT$

$25=5+aT$

$\implies T=20/a$

If the time taken in travelling from P to Q is $t_1$ then

$v'=u+at_1$

$\implies 15=5+at_1$

$\implies at_1=10$

$\implies t_1=10/a$

Therefore, time taken in travelling from Q to R

$t_2=T-t_1=20/1-10/a=10/a$

Ratio

$\frac{t_1}{t_2}=1$

or, $t_1:t_2=1:1$

Hope this helps.

Answer 2

Answer:

(d)1:1

...........................