SATHEE: Motion in a Straight Line

Motion in a Straight Line - Result Question 38

39. A ball is dropped from a high rise platform at $t = 0$ starting from rest. After 6 seconds another ball is thrown downwards from the same platform with a speed $v$ . The two balls meet at $t = 18 s$ . What is the value of $v$ ?

[2010] (take $g = 10 m / s^{2}$ )

(a) $75 m / s$

(b) $55 m / s$

(d) $60 m / s$

Show Answer

Answer:

Correct Answer: 39. (a)

Solution:

(a) Clearly distance moved by $1^{st}$ ball in $18 s =$ distance moved by $2^{nd}$ ball in $12 s$ …(i)

Now, distance moved in $18 s$ by $1^{st}$

ball $= \frac{1}{2} \times 10 \times 18^{2} = 90 \times 18 = 1620 m$

Distance moved in $12 s$ by $2^{nd}$ ball

$= u t + \frac{1}{2} g t^{2} \Rightarrow 12 v + \frac{1}{2} \times 10 \times (12)^{2}$ $\Rightarrow 12 v + 720$

From equation (i)

$∴ 1620 = 12 v + 5 \times 144$

$\Rightarrow v = 135 - 60 = 75 m s^{- 1}$

Play Store

App Store

Ask SATHEE

Welcome to SATHEE !
Select from 'Menu' to explore our services, or ask SATHEE to get started. Let's embark on this journey of growth together! 🌐📚🚀🎓

I'm relatively new and can sometimes make mistakes.
If you notice any error, such as an incorrect solution, please use the thumbs down icon to aid my learning.
To begin your journey now, click on "I understand".

Motion in a Straight Line - Result Question 38

39. A ball is dropped from a high rise platform at t=0 starting from rest. After 6 seconds another ball is thrown downwards from the same platform with a speed v. The two balls meet at t=18s. What is the value of v ?

Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

Menu

39. A ball is dropped from a high rise platform at $t = 0$ starting from rest. After 6 seconds another ball is thrown downwards from the same platform with a speed $v$ . The two balls meet at $t = 18 s$ . What is the value of $v$ ?