Work,Power & Energy-2

1133
Sourish Ghosh ·

(D)

• Akash Anand Its not the right answer..try again.
• Akash Anand Actually answer is given C but I am also getting D. You people try once again.
996
Swarna Kamal Dhyawala ·

12k(5mg/k)2 -12k(3mg/k)2 =12mv2
from here we get v as 4gâˆšmk

• Akash Anand You have not considered the gravitational potential energy.
229
Dwijaraj Paul Chowdhury ·

(D)

• Akash Anand Its not the right answer..try again.
• Akash Anand Actually answer is given C but I am also getting D. You people try once again.
1161
Akash Anand ·

Comment if I am wrong..

12K(6mgk)2=12K(2mgk)2+mg(8mgk)+12mv2

• Sourish Ghosh It should be mg*8mg/k.
• Swarna Kamal Dhyawala cant understand sir plzz explain it
• Dwijaraj Paul Chowdhury Still getting (D)
• Dwijaraj Paul Chowdhury Following sir's formula answer is zero o_O
• Swarna Kamal Dhyawala absolutely according to sir's eqn we get 0 and we correct it as mg*8mg/k then we get answer (D)
• Akash Anand @Sourish ..you are right...it was a typing mistake..now this is the correct expression.
• Akash Anand For those who did not get this expression.. In left hand side its the total initial spring potential energy (Since as equilibrium position spring was compressed already) In right hand side this is the final spring potential energy(expansion in the spring can be found out from other condition in the question)+gain in gravitational potential energy(taking reference the compressed position as zero potential energy)+kinetic energy.
• Dwijaraj Paul Chowdhury But sir can we do this?
229
Dwijaraj Paul Chowdhury ·

let instantaneous extension be x' at time t=02
considering 3m block...having mg as normal reaction....
kx'+mg=3mg
kx'=2mg
x'=2mg/k
now...
(kx'^2)/2+(mv^2)/2 =0
taking mod value...nd solving v... we get v as 2g root (m/k)