Question

The driver of a car moving towards a rocket launching pad with a speed of 6 $m{s}^{-1}$ observed that the rocket is moving with a speed of 10 $m{s}^{-1}$ the upward speed of the rocket as seen by the stationary observer is

• A. 4 $m{s}^{-1}$
• B. 6 $m{s}^{-1}$
• C. 8$m{s}^{-1}$
• D. 11 $m{s}^{-1}$

Answer 1

The correct option is D 11 $m{s}^{-1}$

Given data,

$V_{RC}=10m{s}^{-1}$

$V_C=6m{s}^{-1}$

$V_R=?$

$V_R=\sqrt{V_c^2+V_{RC}^2-2V_c{V}_{RC}cos{90}^0}$

$V_R=\sqrt{{10}^2+6^2}$

$V_R=\sqrt{100+36}$

$V_R=\sqrt{136}=11m{s}^{-1}$

the upward speed of the rocket as seen by the stationary observer is $11m{s}^{-1}$