Question

A ball is thrown vertically upward with a speed of 120m/s. It's speed at midpoint of it's path is about ( g=10)
1. 96.2 m/s
2. 84.6 m/s
3. 75 m/s
4. 60 m/s

Answer 1

Hey dear,

◆ Answer-
(2) v = 84.8 m/s

◆ Explaination-
# Given-
u = 120 m/s
g = 10 m/s^2

# Solution-
Using Newton's 2nd Kinematics eqn-
v^2 = u^2 + 2as

Here, v = 0, u = 120 m/s, a = -g & s = h, hence
0 = 120^2 - 2×10×h
h = 14400 / 20
h = 720 m

At half this distance, s = h/2 = 360 m,
v^2 = u^2 + 2as
v^2 = 120^2 - 2×10×360
v^2 = 14400 - 7200
v^2 = 7200
v = 84.85 m/s

Velocity of body at midpoint of its path is 84.85 m/s.

Hope this helps you..

Answer 2

The speed of the ball at midpoint of it's path is about 84.6 m/s

Explanation:

Given Data

Speed of the ball = 120 m/s

Gravity = 10 m/s²

To find the speed of the ball at it's midpoint

The equation for Newton's second law of Kinematics is

v² + u² = 2(as)  -------- (1)

Let us consider that a = - g and s = h

Substitute the respective values in equation (1) where v = 0

v² + u² = 2(as)

0² + (120)² = 2 (-g)(h)

0 + 14400 = 2 (-10) (h)

14400 = 20 (h)

$h = \frac{14400}{2}$

h = 720 m  

Height 'h' = 720 m

At the midpoint $s = \frac{h}{2}$

$s = \frac{720}{2}$

s = 360 m

Substitute s = 360, u = 120 m/s, and a= -g in equation (1)

v² + u² = 2(as)

v² + (120)² = 2 (-10)(360)

v² = 14400 - 7200

v² = 7200

v² = 84.85 m/s

The above answer is approximately equals to 84.6 m/s.

Therefore the speed of the ball at midpoint of it's path is about 84.6 m/s when it is thrown vertically upward with a speed of 120 m/s

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