KEAM 2014 Physics and Chemistry Paper

Given, Initial velocity, U=v
Final velocity, V=‌

V

2

Distance, s=20cm
Let, the further distance of penetration before it comes to rest be x.
V2=U2−2as
(‌

v

2

)2=v2−2a×20
40a=v2−‌

v2

4

40a=‌

3v2

4

....(i)
and v2=u2+2as
v2=0+2a×(20+x)
v2=2×‌

3

160

v2×(20+x)  [From Eq. (i)]
1=‌

3

80

(20+x)
‌

80

3

=20+x
x=‌

80

3

−20
x=‌

80−60

3

x=‌

20

3

=6.66cm