Respuesta :
First the stone will move upward till reach maximum height, when it will start to go down till hit the ground. So to calculate the time going up, we can use equation:
Vf = Vi + a*t , where Vf is final speed, Vi is initial speed, a is acceleration and t is time
In this case a = -g = -9.81 m/s^2 because the stone goes against gravity attraction.
0 = 6.71 - 9.81*t => t = 6.71/9.81 = 0.68 seconds
And the distance upward will be:
d = Vi*t + 1/2*a*t^2 = 6.71*0.68 + 1/2*(-9.81)*0.68^2
d = 4.59-2.29 = 2.29 metres
Then the stone starts to go down till the ground, which is 18.9 + 2.29 metres below
and it takes, now a = g = 9.81 m/s2 because stone goes in the same direction than gravity atraction:
d = Vi*t + 1/2*a*t^2 => 0*t+1/2*9.81*t^2 => 21.19 = 4.905*t^2 => t = 2.08 seconds
So then the stone is on air 0.68 seconds going up and 2.08 going down, that is in total: 2.76 seconds
A) The speed at which the stone impacts the ground is; v = 20.39 m/s
B) The time at which the stone is in the air is; t = 1.39 s
We are given;
Initial velocity; u = 6.71 m/s
Distance; s = 18.9 m
Acceleration due to gravity; g = 9.81 m/s²
To calculate the speed at which the stone impacts the ground, we will use newtons' third equation of motion which is;
v² = u² + 2gs
Where;
v = final velocity
u = initial velocity
a = acceleration due to gravity
s = distance
A) Plugging in the relevant values gives;
v² = 6.71² + 2(9.81 × 18.9)
v² = 415.8421
v = √415.8421
v = 20.39 m/s
2) We can find the time at which the phone is in the air using newton's first equation of motion which is; v = u + gt
Plugging in the relevant values gives;
20.39 = 6.71 + 9.81t
9.8t = 20.39 - 6.71
9.81t = 13.68
t = 13.68/9.81
t = 1.39s
Read more at; https://brainly.com/question/18951081
