Kinetic energy = (1/2) (mass) x (speed)²
At 7.5 m/s, the object's KE is (1/2) (7.5) (7.5)² = 210.9375 joules
At 11.5 m/s, the object's KE is (1/2) (7.5) (11.5)² = 495.9375 joules
The additional energy needed to speed the object up from 7.5 m/s
to 11.5 m/s is (495.9375 - 210.9375) = <em>285 joules</em>.
That energy has to come from somewhere. Without friction, that's exactly
the amount of work that must be done to the object in order to raise its
speed by that much.
Answer:

I'm just in jss2 but I read physics. this is what I think
Answer:
The balloon will continue to expand and eventually burst.
Explanation:
Simply, the reason for this is because the density of the atmosphere decreases gradually as you increase in altitude closer to space. This means that the air on the outside of the balloon can't provide enough pressure over the surface of the balloon in order to counteract the gas on the inside of the balloon from expanding.