Answer:
The height of the object after 3 seconds is 45 feets.
Explanation:
The height of an object thrown into the air with an initial upward velocity of 63 feet per second is given as
![h(t)=-16t^2+63t](https://img.qammunity.org/2019/formulas/mathematics/high-school/vjcqu9e748wfnt3nixeo1or6y74ajjjxzt.png)
Where, h(t) is height of the object in feet and t is the time in seconds.
We have to find the height of the object after 3 seconds. So, substitute t=3.
![h(3)=-16(3)^2+63(3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/enxx2unjifon02n20l85xw8w3wtjd0agsf.png)
![h(3)=-16(9)+189](https://img.qammunity.org/2019/formulas/mathematics/high-school/zo25oepnhteff5pol9pas10zjl1lygo7s4.png)
![h(3)=-144+189](https://img.qammunity.org/2019/formulas/mathematics/high-school/zq7nddjl6tge5pa0o4xeg59ctqnp6q7k1y.png)
![h(3)=45](https://img.qammunity.org/2019/formulas/mathematics/high-school/1on5ye6dt1m7f4wnpeoc4k8nc4yw85nq10.png)
Therefore height of the object after 3 seconds is 45 feets.