b) intervalul de timp t3 in care prin fata sa trece vagonul urmator
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Answer:
3.6 m
Explanation:
let x = horizontal distance between emily and allison should be for allison to catch the ball
Find horizontal speed of the ball
vx = 12 sin 30 = 12 x 0.5 = 6 m/s
To find time taken, we will use vertical values of the ball motion
Initial velocity in vertical direction
u = 12 cos 30 = 10.392 m/s
let a = g = 9.8m/s2
Use equation of motion
s = ut +1/2at^2
s = vertical distance = 8
8 = (10.392)t + (1/2)(9.8)t^2
8 = (10.392)t + (4.9)t^2
4.9t^2 + 10.392t - 8 = 0
Using formula of quadratic or calculator, we'll find
t = 0.6 and t = -2.72
We pick t=0.6s since it's not logical time in negative
Assuming no air resistance or external forces, the ball will move 6m/s horizontally. Hence using the formula of speed
speed vx = distance x / time
x = (vx)(t)
= 6 x 0.6
= 3.6 m
A. a child gently swinging on a swing at small angles all the time
The Energy is Kinetic Energy.
Kinetic Energy = 1/2*mv², Where m is mass in kg, v is velocity in m/s
Energy is 33750 Juoles, v = 30m/s
1/2*mv² = E
1/2*m*30² = 33750
m = (2*33750) / (30²) Using a calculator
m = 75 kg
Mass of object is 75 kg.