Question

a car is moving a straight line with initial velocity 5m/s.after time 10 sec its velocity becomes 20m/s.calculate the acceleration. then apply brakes it comes to rest. after time 20s. calculate the acceleration i this case also​

Answer 1

Step-by-step explanation:

1st case:

u = 5m/s

v = 10m/s

t = 10s

a= v-u/t

a = 10-5/10

a = 5/10

$a = 0.5m \ {s}^{2}$

2nd case :

u = 5 m/s

v= 0 m/s

t = 20 s

a = v-u/t

a = 0-5/20

a = -5/20

$a = -0.25m \: {s }^{2}$

Answer 2

Given :-

Initial velocity u = 5 m/s

Final velocity v = 20 m/s

Time taken for acceleration = 10 s

Time taken for coming down to rest = 20 s

To Find :-

The acceleration in case 1 and in case 2 respectively.

Solution :-

$\huge{\sf{\underline{\underline{\blue{Case\: one}}}}}$

u = 5 m/s, v = 20 m/s , t = 10s

From the first equation of motion

We have :-

$\huge{\red{\boxed{V\: =\: u\: +\: at}}}$

On inserting the values in the formula

We have :-

20 = 5 + a × 10

=> 10a = 20 - 5

=> 10a = 15

$\implies\: a\: =\: {\dfrac{\not{15}^{3}}{\not{10}^{2}}}$

=> a = 1.5

: acceleration = 1.5 m/s²

$\huge{\sf{\underline{\underline{\blue{Case\: two}}}}}$

u = 20 m/s, v = 0 m/s, t = 20s

From the first equation of motion

We have :-

$\huge{\red{\boxed{V\: =\: u\: +\: at}}}$

On inserting the values in the formula

We have :-

0 = 20 + a × 20

=> 20a = -20

$\implies\: a\: =\: {\dfrac{-20}{20}}$

=> a = -1

: acceleration = -1 m/s²

Required answer = 1.5m/s² and -1 m/s²