please answer all of the following questions

$7.$ If an object weighing $196$ N has a kinetic energy of $950$ J$,$ what is its velocity?

Use the information to answer the following question

A $50\mathrm{.}0$ kg carton is dragged up a low$-$friction plank onto the back of the truck. The length of the plank is $3\mathrm{.}00$ m and it makes an angle of $15\mathrm{.}0$ with the ground.

$9.$ With respect to the bottom of the plank, the gravitational potential energy of the carton on the truck is

$10.$ Calculate the gravitational potential energy of an $15\mathrm{.}8$ kg object sitting on a table

$2\mathrm{.}10$ m above the floor.

$12.$ If a force of $256$ N is applied to a spring, the spring is stretched a distance of $9\mathrm{.}50$ cm from its equilibrium position. What is the elastic constant of this spring?

$13.$ A spring with an elastic constant of $4\mathrm{.}50$ x $10^3$N$/$m is stretched to a position $7\mathrm{.}50$ cm from its equilibrium position. What is the increase in the energy stored in this spring if it is stretched another $5\mathrm{.}00$ cm$?$

$14.$ A child, initially at rest at the top of $3\mathrm{.}55$ m high slide, slides down to a height of $0\mathrm{.}480$ m$.$ At the bottom of the slide, the child has a speed of $2\mathrm{.}45$ m$/$s$.$ If the mass of the child is $34\mathrm{.}5$ kg$,$ what is the change in mechanical energy of the child?

$17.$ If a $70\mathrm{.}0$ kg student runs up a flight of stairs $15\mathrm{.}0$ m high in $25\mathrm{.}0$ s$,$ what is the average power?

$18.$ A $65\mathrm{.}0$ kg student climbs a set of stairs in $25\mathrm{.}0$ s with a power output of $95$ W$.$ What is the vertical height of the stairs?