Question

3. An object is thoown vestically upwards and rises to a heigh of 20m. Then the velocity with which the object was thrown upward is (g=10m/s2).
Option A : 15m/s
Option B: 25m/s
Option C: 10m/s
Option D : 20m/s

Please give me answer with process please​

Answer 1

Given :

• Height reached by object = 20 m
• Gravitational acceleration = 10 m/s²

To find :

• Initial velocity of object

Solution :

Given values ; height (h) = 20 m . Gravitational acceleration (g) = 10 m/s²

As the object is vertically thrown upwards and we know at maximum height final velocity of an object is 0 , therefore ;

✴ H = u²/2g

⇒ 20 = u²/(2 × 10)

⇒ 20 = u²/20

⇒ u² = 20 × 20

⇒ u² = 400

⇒ u = √400

⇒ u = 20 m/s  [Option D]✴

∴ Object was thrown upwards with a velocity of 20 m/s

Answer 2

Answer:

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• Height ( h ) = 20 m
• Final Velocity ( v ) = 0 m/s [As Object will be at rest after attending maximum height]
• Acceleration due to Gravity ( g ) = - 10 m/s²
• Initial Velocity ( u ) = ?

⠀

$\underline{\bigstar\:\textsf{Using Third Equation of Gravity :}}$

$:\implies\sf (v)^2-(u)^2=2gh\\\\\\:\implies\sf (0)^2-(u)^2=2 \times (-10) \times 20\\\\\\:\implies\sf -(u)^2= - 400\\\\\\:\implies\sf (u)^2= 400\\\\\\:\implies\sf u = \sqrt{400}\\\\\\:\implies\underline{\boxed{\sf u = 20\:m/s}}$

⠀

$\therefore\:\underline{\textsf{Ball was thrown with c) \textbf{20 m/s} velocity}}.$