Question
A projectile is launched straight up from the ground with an initial velocity of 120ft/s If acceleration due to gravity is - 16ft/s^2 after about how many seconds will the object reach a height of 200 ft? h(t)=at^2+vt+h_(0) 1:0 s 1.7 s 2.5 s 8.0 s
Answer
4.6
(161 Votes)
Ella
Professional · Tutor for 6 years
Answer
###
Explanation
## Step1: Identify the known and unknown variables### The given initial velocity is
, the height to reach is
, and the acceleration due to gravity is
. We need to determine the time
.## Step2: Write the height equation### The height equation for projectile motion is \( h(t) = a t^2 + v_0 t + h_0 \). Here
since the object is launched from the ground level.## Step3: Substitute the known values into the height equation### Substitute
,
,
, and
into the equation:
## Step4: Solve the quadratic equation### Rearrange the equation to standard quadratic form:
Divide the entire equation by 4 for simplicity:
Use the quadratic formula
where
,
, and
:Calculate the discriminant:
Find the roots:
This gives two solutions:
## Step5: Select the feasible time### Since 5 seconds seems impractically long for the object to ascend and still be rising, select the smaller, realistic time value.#