# Please help me understand my Math?

1. A tennis ball is launched with an initial velocity of 24.5 m/s from the edge of a cliff that is 117.6 meters above the ground. Which quadratic equation could be used to correctly determine when the ball will hit the ground:

4.9t2 + 24.5t + 117.6 = 0

-4.9t2 - 24.5t + 117.6 = 0

-4.9t2 + 24.5t - 117.6 = 0

4.9t2 + 24.5t - 117.6 = 0

-4.9t2 + 24.5t + 117.6 = 0

2. Solve the equation you chose in question 1 to determine when the ball will hit the ground. (HINT: If you don't get one of the answers listed for this question, then maybe you chose the wrong equation in #18. Use this opportunity to double check your work!)

t = 8 seconds

t = 4 seconds

t = 3 seconds

t = -3 seconds

The ball will never reach the ground.

please help me understand how to solve these. I don't understand, please help me. Thank you so much!

4.9t2 + 24.5t + 117.6 = 0

-4.9t2 - 24.5t + 117.6 = 0

-4.9t2 + 24.5t - 117.6 = 0

4.9t2 + 24.5t - 117.6 = 0

-4.9t2 + 24.5t + 117.6 = 0

2. Solve the equation you chose in question 1 to determine when the ball will hit the ground. (HINT: If you don't get one of the answers listed for this question, then maybe you chose the wrong equation in #18. Use this opportunity to double check your work!)

t = 8 seconds

t = 4 seconds

t = 3 seconds

t = -3 seconds

The ball will never reach the ground.

please help me understand how to solve these. I don't understand, please help me. Thank you so much!

The formula to use is s = ut + .5(at^2)

s = distance

u = initial velocity

a = acceleration

t = time

s = ut + .5(at^2)

s = distance = height = 117.6 m

u = initial velocity = 24.5

a = acceleration = acceleration due to gravity = 9.8 ms^-2

t = time = unknown

Now solving (please see first source for calculation for verification)

we have

4.9t2 + 24.5t - 117.6 = 0

or

t = 3, -8

and ignoring the negative answer (taking only the positive answer), we have

t = 3 seconds which is the required time.

Note: The question fails to mention that the ball is shot vertically down towards the ground with the initial velocity. Maybe that threw you off.

The solution is accurate to my knowledge. However, I strongly recommend that you try this question again by yourself to make sure there were no silly errors.

s = distance

u = initial velocity

a = acceleration

t = time

s = ut + .5(at^2)

s = distance = height = 117.6 m

u = initial velocity = 24.5

a = acceleration = acceleration due to gravity = 9.8 ms^-2

t = time = unknown

Now solving (please see first source for calculation for verification)

we have

4.9t2 + 24.5t - 117.6 = 0

or

t = 3, -8

and ignoring the negative answer (taking only the positive answer), we have

t = 3 seconds which is the required time.

Note: The question fails to mention that the ball is shot vertically down towards the ground with the initial velocity. Maybe that threw you off.

The solution is accurate to my knowledge. However, I strongly recommend that you try this question again by yourself to make sure there were no silly errors.