- Home
- Standard 12
- Physics
11.Dual Nature of Radiation and matter
medium
An astronaut floating freely in space decides to use his flash light as a rocket. He shines a $10$ watt light beam in a fixed direction so that he acquires momentum in the opposite direction. If his mass is $80$ kg, how long must he need to reach a velocity of $1$ $ms^{-1}$
A
$9$ sec
B
$2.4 \times 10^3\, sec$
C
$2.4 \times 10^6 \,sec$
D
$2.4 \times 10^9\,sec$
Solution
(d) Let it take $t$ sec for astronaut to acquire a velocity of $1 ms ^{-1}$.
Then energy of photons = $10\, t$
Momentum $ = \frac{{10t}}{C}$ = $80 \times 1$
$t = \frac{{80 \times 1 \times 3 \times {{10}^8}}}{{10}} = 2.4 \times {10^9}\,sec$
Standard 12
Physics
