Answer:
(a) 8 m/s
(b) 5 s
Explanation:
(a)
Using newton's equation of motion,
v² = u²+2gs ..................... Equation 1
Where v = final velocity, u = initial velocity, g = acceleration due to gravity at the surface of moon, s = height reached.
make u the subject of the equation,
u² = v²-2gs
u = √(v²-2gs)................ Equation 2
Note: As the stone is thrown up, v = 0 m/s, g is negative
Given: v = 0 m/s, s = 20 m, g = -1.6 m/s²
Substitute into equation 2
u = √(0-2×20×[-1.6])
u = √64
u = 8 m/s.
(b)
Using,
v = u+ gt
Where t = time of flight to reach the maximum height.
Make t the subject of the equation,
t = (v-u)/g................................... Equation 3
Given: v = 0 m/s, u = 8 m/s, g = - 1.6 m/s²
Substitute into equation 3
t = (0-8)/-1.6
t = -8/-1.6
t = 5 seconds.
