What is the gravitational potential energy of the obectj

[pola]

hi, please help me figure these problems out. much appreciated.

1. an object of mass .7kg is thrown vertically upwards at a speed of 29 m/s. What is the gravitational potential energy of the obect at the highest point of its trajectory?

2. an object of mass 8.9kg moves with initial speed 21 m/s then interacts with its environment, gaining 1.6J of energy. What is the speed of the object after after the interaction is completed?

 

[pixel01]

1. You have to consider the gravitational potential at the start point as zero. Then the potential at the highest point equals to the dynamic energy of the object or:

E = 1/2mv^2.

2. After the interaction, the dynamic energy is reduced by 1.6J. You can calculate the speed reduction via equ. deltaE=1/2m(deltav)^2. Then the final speed is known by a subtraction