)the best rebounders in basketball have a vertical leap (that is, the vertical movement of a fixed point on their body) of about 120 cm. (a) what is their initial "launch" speed off the ground? (b) how long are they in the air?

Let u = the vertical launch speed.

Neglect air resistance, and g = 9.8 m/s².

At the maximum height of h = 120 cm = 1.2 m, the vertical velocity is zero.
Therefore
(u m/s)² - 2*(9.8 m/s²)*(1.2 m) = 0
u² = 23.52 (m/s)²
u = 4.85 m/s

The time to attain maximum height is one half of the travel time.
If t = time to attain maximum height, then
u - gt = 0
4.85 - 9.8t = 0
t = 4.85/9.8 = 0.495 s
Therefore the travel time is 2*0.0495 = 0.99 s

Answers:
(a) 4.85 m/s
(b) 0.99 s

The duration of a photographic flash is related to an rc time constantly

Answerthe energy required is 1.60 × 10⁻¹⁸ j, to three significant figures.explanationwe define electric potential as the ratio electric potential energy to the charge,    then the following gives us the potential difference,      the formula  may be on your formula sheet.the change in electric potential energy would be the energy that would needed to move it from point a to point b. solving for that, we get    using q = 8.00  × 10⁻¹⁹ c and  δv = 2.00 v, we get    the energy required is 1.60 × 10⁻¹⁸ j, to three significant figures.