Question

a ball is dropped from a tower of height 35x m. if in the last 2 seconds of its fall the ball covered 120 m. find x.​

Answer 1

Explanation:

Let the ball dropped down is a and the ball thrown up is b. also the stone thrown upwards cover a distance of x and the other covers a distance of (100 –x).

For ball a

u=0

g=10m/s

2

d=(100−x)

Using the equation

s=ut+

2

1

at

2

100−x=5t

2

.........(1)

For ball b

d=x

g=−10m/s

2

u=25m/s

s=ut+

2

1

at

2

x=25t−5t

2

............(2)

Solving equation (1) and (2)

100=25t

t=4seconds

Put the value of t in equation (1)

x=100−80

x=20m

They will meet at distance of 80 m from the ground after t = 4 seconds

Answer 2

Let the ball dropped down is a and the ball thrown up is b. also the stone thrown upwards cover a distance of x and the other covers a distance of (100 –x).

For ball a

u=0

g=10m/s

2

d=(100−x)

Using the equation

s=ut+

2

1

at

2

100−x=5t

2

.........(1)

For ball b

d=x

g=−10m/s

2

u=25m/s

s=ut+

2

1

at

2

x=25t−5t

2

............(2)

Solving equation (1) and (2)

100=25t

t=4seconds

Put the value of t in equation (1)

x=100−80

x=20m

They will meet at distance of 80 m from the ground after t = 4 seconds