CBSE Questions for Class 9 Physics Force And Laws Of Motion Quiz 16 - MCQExams.com

Newton’s second law of motion says that the mass of object times its acceleration is equal to the net force on the object. Which of the following gives the correct units for force?
  • $$kg.m/s^{2}$$
  • $$kg.m^{2}/s^{2}$$
  • $$kg/m.s^{2}$$
  • $$kg.m^{2}/s$$
  • None of those answer
A body of mass $$10\ kg$$ undergoes a change in velocity of $$10\ m/s$$ in $$5\ s$$. What is the force acting on it?
  • $$100\ N $$
  • $$25\ N $$
  • $$50\ N $$
  • $$20\ N $$
When a bus starts suddenly, the passengers are pushed back. This is an example of which of the following?
  • Newton's first law
  • Newton's second law
  • Newton's third law
  • None of Newton's laws
A force produces an acceleration of $$5.0 \:cm \:s^{-2}$$ when it acts on a body of mass 20 g. Find the force acting on the body.
  • $$2\times 10^{-3}N$$
  • $$4\times 10^{-3}N$$
  • $$1.0\times 10^{-3}N$$
  • $$5\times 10^{-3}N$$
In the above figure, a locomotive has broken through the wall of a train station. During the collision, what can be said about the force exerted by the locomotive on the wall?

1863248_2006156e203b4cd398017a93ebf03196.png
  • The force exerted by the locomotive on the wall was larger than the force the wall could exert on the locomotive.
  • The force exerted by the locomotive on the wall was the same in magnitude as the force exerted by the wall on the locomotive.
  • The force exerted by the locomotive on the wall was less than the force exerted by the wall on the locomotive.
  • The wall cannot be said to “exert” a force; after all, it broke.
An athlete jumps straight up in the air to catch a ball. If he took $$0.4$$ seconds to jump up and $$0.4$$ seconds to come back down, how high did he jump? Take $$g = 9.8\ m/s^{2}$$.
  • $$0.784\ m $$
  • $$1.568\ m $$
  • $$2.352\ m $$
  • $$3.136\ m $$
A gun of mass 1000kg fires a shell of mass 2 kg with a velocity of 200 m/s Calculate velocity of recoll of the gun
  • $$4 m/s$$
  • $$0.2 m/s$$
  • $$0.4 m/s$$
  • None of these
Which of these examples can be explained by Newtons first law of motion ?
  • It is easier to push an empty shopping cart than a full shopping cart
  • It takes a smaller force to roll a marble than a bowling ball
  • When a person steps forward, he exerts a backward force on ground
  • A runner does not come to a stop immediately upon crossing the finish line
A bullet of mass A and velocity B is fired into a block of wood of mass C. If loss of any mass and friction be neglected, then velocity of the system must be
  • $$ \dfrac{AB}{A+C}$$
  • $$ \dfrac{A + C}{B+C}$$
  • $$ \dfrac{AC}{B+C}$$
  • $$ \dfrac{A+B}{AC}$$
 A shell of mass 100 g moving with the speed of $$50 m s^{-1}$$ along a straight line bursts into two pieces. The piece of mass 60 g starts moving horizontally with a speed of $$50 m s^{-1}$$. The other piece moves with a speed of
  • $$50 m s^{-1}$$ opposite to the first piece.
  • $$100 m s^{-1}$$ in vertically downward direction.
  • $$50 m s^{-1}$$ in the same direction as the first piece
  • zero (remains at rest)
If $$120 N $$ of force is acting on a body with $$6 ms^{-2}$$ acceleration, Its mass is _____________. 
  • $$0.05 Kg $$
  • $$20 Kg $$
  • $$200Kg $$
  • $$720 Kg $$
An engine of mass $$5\times {10}^{4}\ kg$$ pulls a coach of mass $$4\times {10}^{4}\ kg$$. A resistance of $$1\ N$$ per $$100\ kg$$ is acting on both the coach and the engine and if the driving force of the engine is $$4500\ N$$ then the acceleration of the engine and the tension in the coupling will respectively be_________
  • The acceleration of the system (coach$$+$$engine) is $$0.04{m/s}^{2}$$
  • The acceleration of the system (coach$$+$$engine) is $$0.05{m/s}^{2}$$
  • The tension in the coupling is $$2000\ N$$.
  • The tension in the coupling is $$2400\ N$$.
A ball rests upon a flat piece of paper on a table top. The paper is pulled horizontally but quickly towards right as shown. Relative to its initial position with respect to the table, the ball
I. Remains stationary if there is no friction between the paper and the ball.
II. Moves to the left and starts rolling backwards, i.e. to the left if there is a friction between the paper and the ball.
III. Moves forward, i.e., in the direction in which the paper is pulled.
Here, the correct statements is/ are
1277016_de22b0e4645541d6b8b6bf896980234d.png
  • I and II only
  • III only
  • I only
  • II only
Which of the following cannot be explained using Newton's third law of motion? 
  • Working of rocket in the fire crackers
  • Revolution of satellite around a planet
  • Functioning of satellite launch vehicle
  • Walking of a person on ground
A bullet of mass $$50$$ gram is fired from a $$5kg$$ gun with a velocity of $$1km/s$$, the speed of recoil of the gun is
  • $$5m/s$$
  • $$1m/s$$
  • $$0.5m/s$$
  • $$-10m/s$$
In CID serial (on TV ), Abhijeet fires a bullet of mass 100g with a speed of 100 $${ ms }^{ -1 }$$ on a soft plywood of thickness 4 cm. The bullet emerges with 10% of its intial KE. Find the emergent speed of the bullet.
  • 31.62 m/s
  • 30.52 m/s
  • 32.75 m/s
  • 33.84 m/s
A bullet is of mass $$5g$$ is fired at a velocity $$900m{s}^{-1}$$ from a rifle of mass $$2.5kg$$. What is the recoil velocity of the rifle?
  • $$9m{s}^{-1}$$
  • $$180m{s}^{-1}$$
  • $$900m{s}^{-1}$$
  • $$1.8m{s}^{-1}$$
A bomb of mass $$16kg$$ at rest explodes into two pieces of masses $$4kg$$ and $$12kg$$. The velocity of the $$12kg$$ mass is $$4m{s}^{-1}$$. The kinetic energy of the other mass is
  • $$192J$$
  • $$96J$$
  • $$144J$$
  • $$288J$$
A target of mass $$M$$ is moving with a velocity $$u$$. Lead shots, each of mass $$m$$, are fired on it in the opposite direction with a velocity $$v$$. Find the number of bullets required to stop the target.
  • $$\dfrac{Mu}{mv}$$
  • $$\dfrac{mv}{Mu}$$
  • $$\dfrac{(M+m)u}{v}$$
  • $$\dfrac{mu(M+m)}{v}$$
If the action and reaction forces are always equal in magnitude, then these forces
  • will produce accelerations of equal magnitudes.
  • may not produce accelerations of equal magnitudes.
  • produce velocities of equal magnitudes.
  • will not produce accelerations of equal magnitudes
Choose the correct statement from the following:
Weightlessness of an astronaut moving in a satellite is a situation of
  • Zero $$g$$
  • No gravity
  • Zero mass
  • Free fall
Rocket propulsion theory is analogues to-
  • Newton`s third law
  • Relative theory
  • First law of thermodynamics
  • none
A bullet weighing $$50$$ gram leaves the gun with a velocity of $$30m/s$$.the ratio of their momentum is:
  • $$1:1$$
  • $$1:2$$
  • $$2:1$$
  • $$1:3$$
Which of the following statement(s) can be explained by Newton's second law of motion?
  • To stop a heavy body ( say truck), much greater force is needed than to stop a light body ( say motorcycle), in the same time, if they are moving with the same speed.
  • For a given body, the greater speed, the greater the opposing force needed to stop the body in a certain time.
  • To change the momentum ( given ) the force required is independent of time.
  • The same forces acting on two different bodies for same time cause the same change in momentum in the bodies.
A truck is moving on a frictionless surface with uniform velocity of $$10\,m{s^{ - 1}}$$. A leak occurs in the water tank of the truck at the rate of $$2\,{kg^{ - 1}}$$. What is the speed of truck after $$50 \ s$$, if the mass of truck is $$100\,kg$$ and mass of water in the truck initially was $$100\,kg$$?
  • $$20\,m{s^{ - 1}}$$
  • $$10\,m{s^{ - 1}}$$
  • $$5\,m{s^{ - 1}}$$
  • None of these
A force of $$50\ N$$ is required to push a car on a level road with constant speed of $$10\ ms^{-1}$$. The mass of the car is $$500\ kg$$. What forces should be applied to make the car accelerate at $$1\ ms^{-2}$$.
  • $$450\ N$$
  • $$500\ N$$
  • $$550\ N$$
  • $$2500\ N$$
Principle of rocket is based on Newton's $$..........$$ law of motion.
  • first
  • second
  • third
  • none
An object maintains its motion under the continuous application of ________force
  • An unbalanced
  • A balanced
  • A strong
  • A weak
Choose whether true or false:-
A bicycle stops if we stop pedalling.
  • True
  • False
Choose whether true or false:-
Unbalanced forces bring in motion.
  • True
  • False
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