Question

a window is 50 cm long.a stone is falling from height of 40 cm above the window.it crosses the window in?
1)3/7 sec
2)2/7 sec
3)1/7 sec

Ans:1/7 sec​

Answer 1

Answer:

Step-by-step explanation:

Given :

S1 = 40 cm = 0.4 m

S2 = 50 cm = 0.5 m

S=S1+S2 = 0.4+0.5 = 0.9 m = 9/10 m

a = 9.8 m/s2

uinitial = 0

Therefore from 2nd equation of motion ;

s= ut+ ½ ×at2

9/10 = 0×t + ½ × 9.8 × t2

9/10 = 0+4.9×t2

t = √9/√49

t = 3/7 seconds

Answer 2

It is A wrong answer Plz click the heart