A car, which can have constant acceleration of 4 m / s 2 and a constant retardation of 8 m / s 2 is travelling on a high way where maximum speed limit is 72 km / h . It starts froms rest and comes to

Question

A car, which can have constant acceleration of $4 m / s^{2}$ and a constant retardation of $8 m / s^{2}$ is travelling on a high way where maximum speed limit is $72 km / h$ . It starts froms rest and comes to rest in minimum time $t_{1}$ after travelling 300 meter and if there is no speed limit then minimum time taken is $t_{2}$ , to cover the same distance. Then find the value of $\frac{4 t _{1}}{t _{2}}$ .

Answer:

5.00

Solution:

$\frac{20 \times 5}{2} + \frac{2.5 \times 20}{2} + 20 (t_{1} - 7.5) = 300$ $t_{1} = \frac{37.5}{2}$

$\frac{3 t \times ( 4 \times 2 t )}{2} = 300$ $t = 5$ $t_{2} = 15$

TestHub · Accepted Answer

2 20 × 5 ​ + 2 2.5 × 20 ​ + 20 ( t 1 ​ − 7.5 ) = 300 t 1 ​ = 2 37.5 ​ 2 3 t × ( 4 × 2 t ) ​ = 300 t = 5 t 2 ​ = 15

Physics - Kinematics Question with Solution | TestHub

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