In which case have we increased the potential energy u of the system?

a) separating a + and - charge
b) separating two + charges
c) separating two - charges

Aballoon is rising vertically upwards at a velocity of 10m/s. when it is at a height of 45m from the ground, a parachute bails out from it. after 3s he opens his parachute and decelerates ata a constant rate 5m/s.when. (a) what was the height of the parachutist above the ground when he opened his parachute? (b)how far is the parachutist from the balloon at t=3s? (c)with what velocity does the parachutist hit the ground? (d)after how long does the parachutist hit the ground after his exist from the balloon?

Calculate a pendulums frequency of oscillation (in hz) if the pendulum completes one cycle in 0.5s.

You can estimate the degree to which a bond between two atoms is ionic or covalent by calculating the