Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • Engineering
  • A 6kg ball is thrown west at 20 m/s and collides with a 14kg ball while in the air. If the balls stick together in the crash and fall straight down to the ground, what was the velocity of the secon

A 6kg ball is thrown west at 20 m/s and collides with a 14kg ball while in the air. If the balls stick together in the crash and fall straight down to the ground, what was the velocity of the second ball?
 

Option: 1

2.3 m/s east


Option: 2

11.2 m/s downward


Option: 3

4.7 m/s east

 


Option: 4

8.6 m/s east


Answers (1)

best_answer

 

 

 

Law of Conservation of Linear Momentum:

  • As we know, \vec{F}=\frac{d\vec{p}}{dt}, If F=0 then change in momentum=0 ⇒p=constant.

     ? p=p1+p2+p3+......=constant

So,

 

We know that if the balls fell straight down after the crash, then the total momentum in the horizontal direction is zero. Based on conservation of momentum, the initial and final momentum values  must be equal in the vertical direction, as the motion is only in vertical direction. If the final horizontal momentum is zero, then the initial horizontal momentum must also be zero.

p_{i}=p_{f}

\Rightarrow m_{1}v_{1}+m_{2}v_{2}=0

\Rightarrow 6\times 20+14\times v_{2}=0

\Rightarrow v_{2}= - 8.6 m/s

The negative sign tells us the second ball is travelling in the opposite direction as the first, meaning it must be moving east.

Posted by

Devendra Khairwa

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

JoSAA Counselling 2025 LIVE: BTech registration starts at josaa.nic.in for IIT, NIT, IIIT admissions
anam-khan

Kota: 17-year old student from UP preparing for JEE dies of electrocution in hostel
anam-khan

CSAB 2025 counselling dates out for special, supernumerary rounds through JEE Mains

Latest Question