Question

28. A ball is dropped from the top of a roof and the distance covered by it in first four second and in last one second is same. The time of journey is (1) 6 s (2) 6.5 s (3) 7s (4) 8.5 s​

Answer 1

Answer:

Correct option is

A

125

A ball is dropped from the roof of a tower height =h

Total distance covered it in the last seconds of its motion

Solution

The distance covered in first 3 second

s=  

2

1

​

at  

2

 

=  

2

1

​

×10×3  

2

 

=45

If the ball takes in second to fall to ground. The distance covered in nth second

s  

n

​

=u+  

2

g

​

(2n−1)

=0+  

2

10

​

(2×n−1)

=10n−5

Therefore, 45=10n−5

10n=50

n=5

Thereforeh=  

2

1

​

=  

2

1

​

gt  

2

 

=  

2

1

​

×10×25

=125m

Explanation:

Answer 2

Answer:

7 s

Explanation:

mark me as brainlistt