A rugby ball is thrown straight upward with a speed of 30 m/s. (a) How long will it rise? (b) How high will it rise? (c) How long after it leaves the hand will it return to the starting point? (d) When will its speed be 16 m/s?
Answers
Answer:
(a) 3.06 sec
(b) 45.92 m
(c) 6.12 sec
(d) 1.63 sec
Explanation:
(a) Given ,
initial veocity (u) = 30 m/s
Since the ball is moving upwards against gravity e final velocity (v) = 0 m/s and
Acceleration due to gravity (g) = -9.8m/s²
We know: v = u+gt
==> 0 = 30 + (-9.8)t
==> -3/-9.8 = t
==> t = 3.06 sec
Hence the ball will rise for 3.06 sec.
(b) Now; 2gh = v² - u²
==> 2×(-9.8)h = 0 - (30)²
==> h = 900/1.96
==> h = 45.918 m
Hence the ball will rise 45.918 m
(c) Again;
Time taken to reach the highest point = 3.06 sec. Hence total time taken to return to the starting point is : 2 × 3.06 sec
= 6.12 sec
(d) Finally, We have: u = 16 m/s
Hence the time taken to acquire the speed will be ;
v = u + at
0 = 16 + (-9.8)t
- 9.8t = - 16
t = 16/ 9.8
t = 1.63 sec
Hence the req time is 1.63 sec
I Hope i am correct and it helps you :)