CBSE Questions for Class 9 Physics Force And Laws Of Motion Quiz 10 - MCQExams.com

A bullet of mass $$0.01$$ kg is fired from a gun of mass $$5$$ kg with velocity of $$250$$ m/s, calculate the speed with which the gun recoils.
  • 0.50 m/s
  • 0.25 m/s
  • 0.05 m/s
  • 0.025 m/s
Swimming is based on Newton's:
  • First law of motion
  • second law of motion
  • third law of motion
  • law of gravitation
In an elevator moving vertically up with an acceleration 'g' the force exerted on the floor by a passenger of mass M is
  • $$Mg$$
  • $$0.5Mg$$ 
  • Zero
  • $$2Mg$$ 
 The mass of a loaded truck $$10$$ tonnes is going at a speed of $$20 \ kmph$$. A box of mass $$2$$ tonnes slips from it and falls on the road. Find the final velocity of the truck (assume that the power of the engine is constant)?
  • $$2.5\  kmph$$
  • $$25 \ kmph$$
  • $$5.5 \ kmph$$
  • $$3.5\  kmph$$
Two bodies have masses in the ratio $$3 : 4$$. When a force is applied on the first body, it moves with an acceleration of $$6 \ m/s^2$$. How much acceleration will the same force produce in the second body?
  • $$2.25 \  m/s^2$$
  • $$4.5 \ m/s^2$$
  • $$6 \ m/s^2$$
  • $$5 \ m/s^2$$
Suppose a body that is acted on by only two forces, is accelerated. For this situation, mark the correct statement :
( Initial Velocity is non zero and in same direction as acceleration  ) 
  • The body cannot move with constant speed
  • The velocity can never be zero
  • The sum of two forces cannot be zero
  • The two forces must act in the same line
Two identical bullets are fired one by a light rifle and another by a heavy rifle with the same force. Which rifle will hurt the shoulder more and why ?
  • Light rifle
  • Heavy rifle
  • Both of them will hurt equally
  • None of these
A passenger in a moving train tosses a coin which falls behind him. It means that the motion of the train is
  • Accelerated
  • Uniform
  • Retarded
  • Along circular tracks
The inertia of an object tends to cause the object:
  • $$\text to\ increase\ its\ speed$$
  • $$\text to\ decrease\ its\ speed$$
  • $$\text to\ resist\ any\ change\ in\ its\ state\ of\ motion$$
  • $$\text to\ decelerate\ due\ to\ friction$$
STATEMENT - 1 : Gas ejected from rocket will never exert thrust on the rocket if the ejected gas and the rocket move in the same direction.
STATEMENT - 2 : To exert thrust on rocket in its direction of motion, the ejected gas (w.r.t. rocket) must move opposite to the velocity of rocket (w.r.t. ground).
  • Statement-1 is True, Statement-2 is True ;Statement-2 is a correct explanation for Statement-1.
  • Statement-1 is True, Statement-2 is True ;Statement-2 is NOT a correct explanation for Statement-1.
  • Statement-1 is True, Statement-2 is False.
  • Statement-1 is False, Statement-2 is True.
A force of $$5\  N$$ produces an acceleration of 8 $$ms^{-2}$$ on a mass $$m_1$$ and an acceleration of 24 $$m  s^{-2}$$ on a mass $$m_{2}$$ . What acceleration (in $$ms^{-2}$$) would the same force provide if both the masses are tied together?
  • $$4$$
  • $$5$$
  • $$6$$
  • $$7$$
According to the Newton's third law of motion, action and reaction pair:
  • always act on the same body
  • always act on different bodies in opposite directions
  • have same magnitude and directions
  • act on either body at normal to each other
An apple falls from a tree because of gravitational attraction between the earth and apple. If $$F_{1}$$ is the magnitude of force exerted by the earth on the apple and $$F_{2}$$ is the magnitude of force exerted by apple on earth, then
  • $$F_{1}$$ is very much greater than $$F_{2}$$
  • $$F_{2}$$ is very much greater than $$F_{1}$$
  • $$F_{1}$$ is only a little greater than $$F_{2}$$
  • $$F_{1}$$ and $$F_{2}$$ are equal
Suppose a ball of mass m is thrown vertically upward with an initial speed v. Its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momentums of the ball are same. Is this an example of conservation of momentum?
  • Yes
  • No
  • Sometimes
  • None of these
During a planned manoeuvre in a space flight, a free-floating astronaut A pushes another  free floating astronaut B, the mass of A being greater than that of B. Then, the magnitude of the force exerted by astronaut A on astronaut B is:
  • equal to zero
  • equal to the force exerted by B on A
  • greater than the force exerted by B on A
  • less than the force exerted by B on A
What are action-reaction forces?
  • Those which act on the same body.
  • Those which act on different bodies in different directions
  • Those which act vertically.
  • Those which act in the same direction
If action and reaction were to act on the same body then
  • resultant would be zero
  • body would not move at all
  • both (a) and (b)
  • none of these
A body of mass $$300\ g$$ is at rest. What force in Newton will you have to apply to move it through $$200\ cm$$ in $$10\ s$$?
  • Zero
  • $$12\ N$$
  • $$1.2\ N$$
  • $$0.012\ N$$
In a rocket, fuel burns at the rate of $$1\ kg/s$$. This fuel is ejected from the rocket with a velocity of $$60\ km/s$$. Force exerted on  the rocket in $$N$$ is:
  • $$60 N$$
  • $$600 N$$
  • $$6000 N$$
  • $$60000 N$$
Which of the following requires a pushing force?
  • Throwing a stone at a bird.
  • Grabbing hold of a pencil.
  • Leaves falling from a tree.
  • A load lifted by a pulley.
Which of the following units is used to measure thrust?
  • Dyne
  • Pascal
  • Newton per meter square
  • Dyne per centimeter
A man is standing on a boat in still water. If he walks towards the shore the boat will :
  • move away from the shore.
  • remain stationary.
  • move towards the shore.
  • sink.
While dusting a carpet, we give a sudden jerk or beat with a stick because :
  • Inertia of rest keeps the dust in its position and the dust is removed by movement of carpet away.
  • Inertia of motion removes dust.
  • No inertia involved in process.
  • None of the above
In a game of tug of wars, a condition of equilibrium exists. Both the teams pull the rope with a force of 10$$^4$$ N. The tension in the rope is :
  • 10$$^4$$ N
  • 10$$^5$$ N
  • 0 N
  • 2 $$\times $$ 10$$^4$$ N
A force  100 N acts in a body mass 2 kg for 10 s. The change in the velocity of the body is :
  • 100 m s$$^{-1}$$
  • 250 m s$$^{-1}$$
  • 500 m s$$^{-1}$$
  • 1000 m s$$^{-1}$$
Two individual forces of magnitude $$F_1$$ and $$F_2$$ act on a body of mass 1 kg as shown in the figures (i) and (i). If product of net magnitudes of forces produced in fig (i) and (ii) is 27 N then find the magnitude of forces $$F_1$$ and $$F_2$$. (assume $$F_1$$ > $$F_2$$)

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  • 3 N, 6 N
  • 6 N, 6 N
  • 6 N, 3 N
  • 3 N, 3 N
S.I. unit of momentum is :
  • $$kg\ ms^{-1}$$
  • $$kg\ mg^{-2}$$
  • $$kg\ mg^2$$
  • $$kg\ m^{-1}s^{-1}$$
A loaded $$20,000  \ kg$$ coal wagon is moving on a level track at $$6$$ ms$$^{-1}$$. Suddenly $$5000  kg$$ of coal is dropped out of the wagon. The final speed of the wagon is:
  • $$6$$ ms$$^{-1}$$
  • $$8$$ ms$$^{-1}$$
  • $$4.8$$ ms$$^{-1}$$
  • $$4.5$$ ms$$^{-1}$$
The time, in which a force of $$2\ N$$ produces a change as the momentum of $$0.4\ kg ms^{-1}$$ in the body whose mass is $$1\ kg$$ is :
  • $$0.2\ s$$
  • $$0.02\ s$$
  • $$0.5\ s$$
  • $$0.05\ s$$
In case of rocket propulsion choose the correct options.
  • Momentum of rocket always remains constant.
  • Newton's third law is applied.
  • If exhaust velocity and rate of burning of mass is kept constant, then acceleration of rocket will go on increasing.
  • If exhaust velocity and rate of burning of mass is kept constant, then  thrust  force will be constant
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