Question

An object is thrown vertically upwards and rises to a height of 80 m. Calculate the velocity with which the object was thrown upwards? G = 10m/s²
A. 40m/s

B. 50m/s

C. 80m/s

D. 10m/s

The time taken by the object to reach the highest point in the above question.
A. 4s
B. 5s
C. 8s
D. 1s
please helpp​
my exam is going on​

Answer 1

Answer

i)

Given :

• Maxmimum height (h) = 80 m
• Acceleration due to gravity (g) = -10 m/s
• Final velocity (v) = 0 m/s

To find :

• Initial veloicty - u

Solution :-

Calculating Intial velocity (u)

• h = 80m
• g = -10 m/s
• v = 0 m/s

Substituting the value in 3rd equation of motion :-

$\implies\boxed{\sf v^2 = u^2 + 2as}$

$\implies\sf 0 = u^2 + 2 \times (-10) \times 80$

$\implies\sf 0 = u^2 - 1600$

$\implies\sf u^2 = 1600$

$\implies\sf u = 40 m/s$

$\boxed{\rm\red{Inital\: velocity = 40 m/s}}$

Calculating time taken (t)

• u = 40 m/s
• g = -10 m/s
• v = 0 m/s

Substituting the value in 1st equation of motion :-

$\implies\boxed{\sf v = u + at}$

$\implies\sf 0 = 40 - 10t$

$\implies\sf 10t = 40$

$\implies\sf t = \frac{40}{10}$

$\implies\sf t = 4 s$

$\boxed{\rm\red{Time\: taken = 4 sec}}$