Question
SLPaper 1
The height of a baseball after it is hit by a bat is modelled by the function
$$ h(t) = -4.8t^2 + 21t + 1.2 $$where $h(t)$ is the height in metres above the ground and $t$ is the time in seconds after the ball was hit.
1.
Write down the height of the ball above the ground at the instant it is hit by the bat.
[1]Verified
Solution
- State the initial height ($t=0$): $1.2$ metres A1
2.
Find the value of $t$ when the ball hits the ground.
[2]Verified
Solution
- Set expression equal to zero: $-4.8t^2 + 21t + 1.2 = 0$ M1
- Solve for $t$: $t = 4.43 \text{ s}$ $(4.43141\dots \text{ s})$ A1
3.
State an appropriate domain for $t$ in this model.
[2]Verified
Solution
- State the domain: $0 \leq t \leq 4.43$ OR $[0, 4.43]$ A1A1
