Question

An object of mass 20 kg is lifted aganist the gravity at 20m is dropped . find the velocity of the object . when it reached at the point which is 15m above the ground. take g = 10m/s^2


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Answer 1

Given :

Mass of object = 20kg

Height = 20m

Initial velocity = zero

To Find :

Velocity of the object when it reached at the point which is 15m above the ground.

Solution :

❒ For a body falling freely under the action of gravity, g is taken positive.

• Since constant acceleration due to gravity acts on the body, equation of kinematics can be easily applied to solve this question$.$

Here we are asked to find velocity of the object at the point which is 15m above the ground.

• Distance covered from top point will be 20 - 15 = 5m

Third equation of kinematics;

• v² - u² = 2gh

» v denotes final velocity

» u denotes initial velocity

» g denotes acceleration

» h denotes height / distance

By substituting the given values;

➙ v² - 0² = 2 (10) (5)

➙ v² = 100

➙ v = √100

➙ v = 10 m/s

Answer 2

$\large{\underline{\underline{\sf{ \maltese \: {Given:-}}}}}$

• Mass of the object = 20 kg
• Height = 20 m
• Initial velocity (u) = 0 m/s
• Acceleration (g) = 10 m/s²

$\large{\underline{\underline{\sf{ \maltese \: {To \: find:-}}}}}$

• Final velocity (v) = ?

$\large{\underline{\underline{\sf{ \maltese \: {Solution:-}}}}}$

~ Distance Covered From Top Point :

$\qquad \quad {:} \longrightarrow \sf{ \bigg(20 - 15 \bigg)} \: {m}^{2}$

$\qquad \quad {:} \longrightarrow \underline{\boxed{\sf{ 5 \: {m}^{2}}}}$

~ Third Equation of Motion :

$\qquad \bull \: \bf{v² - u² = 2ah}$

$\qquad \quad {: } \longrightarrow \sf{ {v}^{2} - {0}^{2} = 2 \times 10 \times 5 }$

$\qquad \quad {: } \longrightarrow \sf{ {v}^{2} - {0} = 100 }$

$\qquad \quad {: } \longrightarrow \sf{ {v}^{2} = 100 + 0 }$

$\qquad \quad {: } \longrightarrow \sf{ {v}^{2} = 100 }$

$\qquad \quad {: } \longrightarrow \sf{ {v}= \sqrt{100 }}$

$\qquad \quad {: } \longrightarrow \underline{\boxed{\sf{ {v}= 10}}}$

$\qquad \therefore \sf{The \: velocity \: of \: the \: object \: = \: \underline{\underline{10 \: m/s}}}$

$\large{\underline{\underline{\sf{ \maltese \: {Answer:-}}}}}$

• The velocity of the object is 10 m/s