Question

Physics Question:

What is H, the HEIGHT from which the ball is thrown?

From the roof of a tall building, a student throws a ball of mass m = 0.2 kg with initial speed vo = 30 m/s at an angle 20 degrees below the horizontal as shown in the figure. The ball is thrown from a height H above the ground. The student measures the ball to be in the air for 5 seconds before it hits the ground. Ignore air resistance.

Answer 1

Suppose now that we increase both the initial speed (vo) and the initial angle ( θ) such that the horizontal component of the velocity (vocos θ) does not change .

A.tf decreases (tf < 5 s)
B.tf increases (tf > 5 s)
C.tf stays the same (tf = 5 s)

Answer 2

Both are questions from the same scenerio.

Answer 3

hf=hi+vi_yt+1/2at2
hf=0
a= gravity=9.81 m/s^2
Vi_y=Vi sin(20)= 10.26 m/sec
t=5 sec
Vi=30 m/sec

Answer 4

yes

Answer 5

h=10.26*5+.5*9.81*25=387.6 m

Answer 6

what is tf?

Answer 7

but thats not an option...theres only.

a. 51.3
b. 174
c. 273
d. 12.5
e. 150

Answer 8

tf is the total time in the air change

Answer 9

i attached a screenshot of the problem for clarity

Answer 10

i got H=174 your calculation was right, some numbers were just not plugged in!

Answer 11

i am sorry that was a mistake in the calculation

Answer 12

yes

Answer 13

still need help with the tf problem though i cant seem to figure it outt

Answer 14

no worries at all, you helped alot with the calculation! as i was stuck. thank you for that!

Answer 15

if the vi increase and he need vi_1=vi_2 ---> angle will increase which means cos(theta) get less and sin (theta) getting bigger which means vi_y will get bigger ---> less time

Answer 16

i hope that clear for you.....

Answer 17

Yes!

Answer 18

i am off line ......