Question

When a body is projected upwards, which equation holds good? v = u - gt v = u - at v = u + at v = u + gt

Answer 1

$\LARGE{ \underline{ \purple{ \tt{Required \: answer}}}}$

Whenever a body is under free fall, there is two possibilities: It is moving upwards or falling downwards. So, here we are asked about motion of a body moving upwards.

Body moving upwards:

Whenever a body is thrown upwards, it returns to the ground after some time because it is attracted towards the earth due to gravity.

Here,

• Initial velocity is +u
• Acceleration is -g (because acceleration due to gravity will act downwards and the body is moving upwards)
• Let time taken be t

According to 1st equation of motion:

➝ v = u + at

Putting the above values,

➝ v = u + (-g)t

➝ v = u - gt

So, Correct option is:

$\large{ \boxed{ \rm{v = u - gt \: (Option \: A)}}}$

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Other two equations of motion,

• h = ut - 1/2 gt²
• v² = u² - 2gh

Body moving downwards:

Here,

• Initial velocity = -u
• Final velocity = -v
• Acceleration = -g
• Distance travelled = -h

Equations of motion,

• v = u + gt
• h = ut + 1/2 gt²
• v² = u² + 2gh

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Answer 2

$\huge{\underline{\underline{\boxed{\sf{\purple{Answer ࿐}}}}}}$

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Here,

Initial velocity is = +u

Acceleration is = -g

Let time taken be = t

According to 1st equation of motion:

➝ v = u + at

Putting the above values,

➝ v = u + (-g)t

➝ v = u - gt

So, Correct option is:

Option A

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