Question

34. A balloon is at a height of 81 m and is
ascending upwards with a velocity of 12
m/s. A body of 2kg weight is dropped from
it. If g = 10 m/s, the body will reach the
surface of the earth in
(b) 4.025 s
(a) 1.5 s
(d) 6.75s
c) 5.45​

Answer 1

Answer:

hello mates

✅✅✔️✔️✔️

Explanation:

✔️ formula is h= vit +1/2 gt²

h= 81m

v= 12m/sec

g= -10m/sec² constant

t=?

✔️✔️ now put the value

✅✅81=12t+1/2(-10)t²

✔️✅ 81=12t+-5t²

✅✔️ -5t²+12t-81=0

✅✅using quadratic equation

✔️✔️a= -5

✔️✅b=12

✅✔️c= -81

✔️✔️formula -b+_√b²-4ac/2a

✅✅put the value and get answer

✔️✅I think the answer is (D) 5.45sec

Answer 2

$\huge\bold{Answer\:=\:5.45\:sec}$

___________________________

$\huge\bigstar\underline\mathfrak\blue{Explanation}$

Here,

It is Given that,

acceleration (g) = 10 m/s²

initial velocity ( u ) = -12 m/s ( as balloon ascending upwards )

height ( S ) = 81 m

_____________________________

We know that,

S = ut + ½at² ( by second equation of motion )

81 = -12 × t + ½ × 10 × t²

81= -12t + 5t²

5t²-12t-18 = 0

By solving this quadratic equation,

Using splitting middle term method.

5t² -27t + 15t -81 = 0

→ t ( 5t-27)+3( 5t-27 ) = 0

→ (t+3)(5t-27)=0

→t=-3 and t =27/5

Because, time can't be negative,

Therefore, t = 27/5 = 5.4 seconds

___________________________

Hence, Answer :

C). 5.45 sec