A mass 25kg is attached to a spring which is held stretched a distance 120 cm by a force F=300N (Fig. 7-28), and then released. The spring compresses, pulling the mass. Assuming there is no friction, determine the speed of the mass m when the spring returns: (a) to its normal length (x = 0). (b)find the spring constant k?

Explanation:

Spring is stretched by force f to distance

"X"

now here by force balance we can say

f = kx

k = !

now here we will we say that energy stored in the spring will convert into kinetic energy

kx² = mv²

(x² = mv²

now solving above equation we will have

PART 2)

now for half of the extension again we can use energy conservation

ka²-k(x/2)² = 1 {mv²

¾fx=mv²

now the speed is given as

3 fr 4m V=

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

i really dont know but i will try okay.

so i think u would just add all them up and get your answer..