Question

A stone is thrown in vertically upward direction with a velocity of 5 ms-1. If the acceleration of the stone during its motion is 10 ms-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there? A. Height= 1.25 m and time = 0.5 s B. Height: 2.5 m and time = 0.5 s C. Height= 2.5 m and time = 0.05 s D. Height= 1.25 m and time = 0.05 s

Answer 1

Answer:

Explanation:

Solution,

Here, we have

Initial velocity, u = 5 m/s

Final velocity, v = 0

Acceleration, a = 10 m/s²

To Find,

Height attained, s = ?

Time taken, t = ?

According to the 3rd equation of motion,

We know that,

v² - u² = 2as

So, putting all the values, we get

⇒ v² - u² = 2as

⇒ (0)² - (5)² = 2 × 10 × s

⇒ 25 = 20s

⇒ 25/20 = s

⇒ s = 1.25 m.

Hence, the height attained is 1.25 m.

Now, we will find time taken,

According to the 1st equation of motion,

v = u + at

So, putting all the values again, we get

⇒ v = u + at

⇒ 0 = 5 + 10 × t

⇒ 5 = 10t

⇒ 5/10 = t

⇒ t = 0.5 seconds.

Hence, the time taken is 0.5 seconds.

Here, 1st option i.e, Height= 1.25 m and time = 0.5 s is correct.

Answer 2

Question :-

▪ A stone is thrown in vertically upward direction with a velocity of 5 ms-1. If the acceleration of the stone during its motion is 10 ms-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

A. Height= 1.25 m and time = 0.5 s

B. Height: 2.5 m and time = 0.5 s

C. Height= 2.5 m and time = 0.05 s

D. Height= 1.25 m and time = 0.05 s

_______________________________

Given :-

• Initial velocity =5m/s

• Acceleration =10m/s²

• Final velocity =0m/s

_______________________________

To Find:-

• Height attained by stone.
• Time taken by stone.

_______________________________

Solution :-

By using 3rd equation of motion

$v {}^{2} = u {}^{2} + 2as \\ \\ 0 { }^{2} = 5 {}^{2} + 2 \times 10 \times s \\ 0 = 25 + 20 \times s \\ \\ s = \frac{25}{20} \\ \\ s = 1.25m$

∴The distance covered by stone is 1.25m.

And ,

To find time taken by Stone

so,

By using 1st equation of motion

☛ v =u+at

☛ 0=5+10×t

☛ t=5/10

☛ t=1/2

☛ t=0.5s

∴ The time taken by stone is 0.5s

Hence,

option (A) is the correct answer.