Question

7. A ball is gently dropped from a height of 20 m. If its velocity
increases uniformly at the rate of 10 m s?, with what velocity
will it strike the ground? After what time will it strike the
ground?​

Answer 1

Answer:

Let us assume, the final velocity with which ball will strike the ground be ‘v’ and time it takes to strike the ground be ‘t’

Initial Velocity of ball, u =0

Distance or height of fall, s =20 m

Downward acceleration, a =10 m s-2

As we know, 2as =v2-u2

v2 = 2as+ u2

= 2 x 10 x 20 + 0

= 400

ˆ´ Final velocity of ball, v = 20 ms-1

t = (v-u)/a

ˆ´Time taken by the ball to

strike = (20-0)/10

= 20/10

= 2 seconds

Answer 2

Answer:

S,distance=20 m

a,acceleration =10m/s^2

v,final velocity=?

u,initial velocity=0

We know that

v^2-u^2=2aS

v^2-0=2×10×20

400=v^2

v=20m/s

t=?

We know that 

v=u+at

20=0+10t

t=2 sec