Question

If the force on a rocket moving with a velocity of $$300\,m/s$$   is $$345\,N,$$  then the rate of combustion of the fuel is

A. $$0.55\,kg/s$$
B. $$0.75\,kg/s$$
C. $$1.15\,kg/s$$  
D. $$2.25\,kg/s$$
Answer :   $$1.15\,kg/s$$
Solution :
Thrust on the rocket is the force with which the rocket moves upwards. Thrust on rocket at time $$t$$ is given by $$F = - u\frac{{dm}}{{dt}}$$
The negative sign indicates that thrust on the rocket is in a direction opposite to the direction of escaping gases.
Here, velocity of the rocket $$u = 300\,m/s$$
and force $$F = 345\,N$$
∴ Rate of combustion of fuel $$ - \left( {\frac{{dm}}{{dt}}} \right) = \frac{F}{u} = \frac{{345}}{{300}} = 1.15\,kg/s$$

Releted MCQ Question on
Basic Physics >> Impulse

Releted Question 1

The figure shows the position-time $$\left( {x - t} \right)$$  graph of one dimensional motion of a body of mass $$0.4kg.$$  The magnitude of each impulse is
Impulse mcq question image

A. $$0.4Ns$$
B. $$0.8Ns$$
C. $$1.6Ns$$
D. $$0.2Ns$$
Releted Question 2

A rigid ball of mass $$m$$ strikes a rigid wall at $${60^ \circ }$$ and gets reflected without loss of speed as shown in the figure. The value of impulse imparted by the wall on the ball will be
Impulse mcq question image

A. $$mv$$
B. $$2mv$$
C. $$\frac{{mv}}{2}$$
D. $$\frac{{mv}}{3}$$
Releted Question 3

The force $$F$$ acting on a particle of mass $$m$$ is indicated by the force-time graph shown below. The change in momentum of the particle over the time interval from $$0$$ to $$8 s$$  is
Impulse mcq question image

A. $$24\,N{\text{-}}s$$
B. $$20\,N{\text{-}}s$$
C. $$12\,N{\text{-}}s$$
D. $$6\,N{\text{-}}s$$
Releted Question 4

A man of $$50\,kg$$  mass is standing in a gravity free space at a height of $$10\,m$$  above the floor. He throws a stone of $$0.5\,kg$$  mass downwards with a speed $$2\,m{s^{ - 1}}.$$  When the stone reaches the floor, the distance of the man above the floor will be

A. $$9.9\,m$$
B. $$10.1\,m$$
C. $$10\,m$$
D. $$20\,m$$

Practice More Releted MCQ Question on
Impulse


Practice More MCQ Question on Physics Section