Class 11 NEET Physics Motion in a Straight Line Questions

Let h be height of the tower and t is the time taken by the body to reach the ground.
Here, u=0,a=g
∴h=ut+

1

2

gt2 or h=0×t+

1

2

gt2
or h=

1

2

gt2 ....(i)
Distance covered in last two seconds is
40=

1

2

gt2−

1

2

g(t−2)2 (Here ,u=0)
or 40=

1

2

gt2 −

1

2

g(t2+4−4t)
or 40=(2t−2)g or t=3s
From eqn (i), we get
h=

1

2

×10×(3)2 or h=45m