Consider the ball on a string in question 1. Let the mass of the ball be 0.1 kg, the length of the string be 0.7 m and the speed of the ball at the top be 9 m/s. What is the kinetic energy at the bottom?

5.4234  J

Explanation:

Kinetic energy, KE is given by where m is the mass of the ball, v is the velocity.  The potential energy is also transformed to kinetic energy. Considering that potential energy is mgh but in this case part 1 had it as 2mgh then total kinetic energy at the bottom will be

where g is acceleration due to gravity and its value is taken as 9.81, h is the height of string.

that would be because of both gravity and friction. so     c