Answer:
The maximum height it reaches will be 20 m.
The time taken by it to reach the height will be: t = 2 seconds.
Step-by-step explanation:
We know the equation of the motion under gravity
v² - u² = 2gs
u = initial velocity = 20 m/s
v = final velocity = 0 m/s
![s\:=\:h_(max)](https://img.qammunity.org/2021/formulas/physics/high-school/2yvx7o8t8docs5p1f964m6i455vzola5yw.png)
so
![v^(2) \:-\:u^(2) \:=\:2gs](https://img.qammunity.org/2021/formulas/physics/high-school/rq0xwwn5z64si71fl9iw93seuyqfbrpqp1.png)
substituting u = 20 m/s, v = 0 m/s, g = -10 and
![s\:=\:h_(max)](https://img.qammunity.org/2021/formulas/physics/high-school/2yvx7o8t8docs5p1f964m6i455vzola5yw.png)
![\left(0\right)^2-\:\left(20\right)^2=\:2\left(-10\right)* h_(max)](https://img.qammunity.org/2021/formulas/physics/high-school/tu7567h2180h9udf3w6u84jkgu4szgaueh.png)
![2\left(-10\right)* h_(max)=-400](https://img.qammunity.org/2021/formulas/physics/high-school/dkig1ucsw0qdh0xcfrhgfij2clpcydiwyl.png)
![(2\left(-10\right)h_(max))/(-20)=(-400)/(-20)](https://img.qammunity.org/2021/formulas/physics/high-school/jxe1n0fcm9nao99c038nwi39shpoojkh51.png)
m
Therefore, the maximum height it reaches will be 20 m.
We know the equation
u = gt
substitute u = 20, g = 10
20 = 10 × t
t = 20/10
t = 2 seconds
Therefore, the time taken by it to reach the height will be: t = 2 seconds.