Question

starting from rest a car moves with Uniform acceleration till it attains a velocity of 72 km/h in 30 s then it moves with Uniform velocity for some time afterwards is retards and come to state of rest after covering a distance of 50 m if total distance covered in 950m.​

Answer 1

Answer:

=15sec

Explanation:

Avg speed × total times = total distance

20×25=500

Since acceleration in the 1st interval is same as deceleration in the 3rd interval and deceleration is from the same velocity achieved after acceleration, t  

1

​  

=t  

3

​  

 

s  

1

​  

=  

2

1

​  

×5t  

1

2

​  

 

s  

2

​  

=(5t  

1

​  

)t  

2

​  

 

s  

3

​  

=(5t  

1

​  

)×t  

3

​  

−  

2

1

​  

×5×t  

1

2

​  

=(5t  

1

​  

)×t  

1

​  

−  

2

1

​  

×5×t  

1

2

​  

 

s  

1

​  

+s  

2

​  

+s  

3

​  

=5t  

1

​  

t  

2

​  

+5t  

1

2

​  

 

⇒5t  

1

2

​  

+5t  

1

​  

t  

2

​  

=500−−−−1

2t  

1

​  

+t  

2

​  

=25−−−−2

Solving (1 ) and   (2) ⇒t  

1

​  

=5,t  

2

​  

=15sec