The one that's completely submerged is displacing more water, so the buoyant force on it is greater.
The right half will be a new bar magnet of 2cm with north pole on the right side and south pole on teh left.
Answer:

%
%
Explanation:
From the exercise we know two information. The real speed and the experimental measured by the speedometer

Since the speedometer is only accurate to within 0.1km/h the experimental speed is

Knowing that we can calculate Kinetic energy for the real and experimental speed


Now, the potential error in her calculated kinetic energy is:

%
%
5.5 s
Explanation:
The time it takes for the ball to reach its maximum height can be calculated using

since
at the top of its trajectory. Plugging in the numbers,
