NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Physics
- Chapter
- Motion in Two Dimensions
NTA Abhyas 2020 · Physics · Motion in Two Dimensions
A man throws a ball of mass m from a moving plank ( A ). The ball...
A man throws a ball of mass from a moving plank (). The ball has a horizontal component of velocity with respect to ground towards another man standing on stationary plank (), as shown in the figure. The combined mass of plank with man as well as that of plank with the other man is each. the x-y plane represents the horizontal plane which is frictionless. If initially, plank was moving with speed u\overset{^}{i} with respect to ground, then the relative velocity of plank (in ) with respect to plank (after the man on plank catches the ball) minus is
Correct answer
7
Step-by-step solution
By conservation of momentum,
3mu\overset{^}{i} = m ( ucos{37}^{o}\overset{^}{i} + usin{37}^{o}\overset{^}{j} ) + 2m\overset{\to}{{V}_{A}}
= \overset{\to}{{V}_{A}} = \dfrac{11u}{10}\overset{^}{i} - \dfrac{3u}{10}\overset{^}{j}
Similarly = \overset{\to}{{V}_{B}} = \dfrac{4u}{15}\overset{^}{i} + \dfrac{3u}{10}\overset{^}{j}
3mu\overset{^}{i} = m ( ucos{37}^{o}\overset{^}{i} + usin{37}^{o}\overset{^}{j} ) + 2m\overset{\to}{{V}_{A}}
= \overset{\to}{{V}_{A}} = \dfrac{11u}{10}\overset{^}{i} - \dfrac{3u}{10}\overset{^}{j}
Similarly = \overset{\to}{{V}_{B}} = \dfrac{4u}{15}\overset{^}{i} + \dfrac{3u}{10}\overset{^}{j}