13. A ball is thrown vertically upwards with a velocity of 49 m/s.
Calculate
(i) the maximum height to which it rises,
(ii) the total time it takes to return to the surface of the earth.
Answers
Explanation:
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Answer:
Explanation:
According to the equation of motion under gravity:
v2 - u2 = 2gs
Where,
u = Initial velocity of the ball
v = Final velocity of the ball
s = Height achieved by the ball
g = Acceleration due to gravity
At maximum height, final velocity of the ball is zero, i.e., v= 0
u = 49 m/s
During upward motion, g = -9.8 m s-2
Let h be the maximum height attained by the ball.
Hence,
0 - 492 = 2×9.8×h
⇒ h = 492/(2×9.8)
⇒ h = 2401/19.6 = 122.5
Let t be the time taken by the ball to reach the height 122.5 m, then according to the equation of motion:
v = u + gt
We get,
0 = 49 + t x (- 9.8)
9.8t = 49
t = 49 / 9.8 = 5s
Also,
Time of ascent = Time of descent
Therefore, total time taken by the ball to return = 5 + 5 = 10 s