9th Class Science Force and laws of motion Question Bank

done Case Based MCQs - Force and Laws of Motion Total Questions - 25

• question_answer1)

  Read the following and answer any four questions from [1] to [6].

  Newton farther studied Galileo's ideas on force and motion and presented three fundamental laws that govern the motion of objects. These three laws are known as Newton's laws of motion. The first law of motion is stated as:

  An object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.

  In other words, all objects resist a change in their state of motion. In a qualitative way, the tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called inertia. This is why, the first law of motion is also known as the law of inertia.

  A football and a stone has same mass, then both will have
  A)
  same inertia done clear
  B)
  same momentum done clear
  C)
  different inertia                           done clear
  D)
  different momentum done clear
  View Solution play_arrow

• question_answer2)
  The inertia of a moving object depends on
  A)
  mass of object                            done clear
  B)
  momentum of object done clear
  C)
  speed of object done clear
  D)
  shape of object done clear
  View Solution play_arrow

• question_answer3)

  When a rubber ball held between hands is pressed, its shape changes.

  This happens because

  A)
  balanced forces act on ball done clear
  B)
  unbalanced forces act on ball done clear
  C)
  frictional forces act on ball done clear
  D)
  gravitational force acts on ball done clear
  View Solution play_arrow

• question_answer4)

  There are two statements

  A. Newton's first law is valid for the pilot in an aircraft which is taking off.

  B. Newton's first law is valid for the observer in a train moving with constant velocity.

  Which of the following is correct?

  A)
  A only                                       done clear
  B)
  B only done clear
  C)
  Both A and B                             done clear
  D)
  None of the above done clear
  View Solution play_arrow

• question_answer5)
  A water tanker filled upto \[\frac{1}{3}\]of its height is moving with a uniform speed. On a sudden application of brakes, the water in the tank would
  A)
  move backward                          done clear
  B)
  move forward done clear
  C)
  be unaffected                             done clear
  D)
  rise upwards done clear
  View Solution play_arrow

• question_answer6)

  Read the following and answer any four questions from [6] to [10].

  While catching a fast moving cricket ball, a fielder in the ground gradually pulls his hands backwards with the moving ball. In doing so, the fielder increases the time during which the high velocity of the moving ball decreases to zero.

  Thus, the acceleration of the ball is decreased and therefore the impact of a catching the fast moving ball (see figure) is also reduced.

  If the ball is stopped suddenly then its high velocity decreases to zero in a very short interval of time.

  Thus, the rate of change of momentum of the ball will be large. Therefore, a large force would have to be applied for holding the catch that may hurt the palm of the fielder.

  A fielder pulls his hands gradually with the moving ball while holding a catch

  Why a fast moving cricket ball can cause more injuries to a cricketer than a moving tennis ball?
  A)
  Due to large force done clear
  B)
  Due to large velocity done clear
  C)
  Both [a] and [b] done clear
  D)
  None of the above done clear
  View Solution play_arrow

• question_answer7)
  Momentum of a bullet of mass 0.2 kg moving at 400 m/s will be
  A)
  4 kg m/s done clear
  B)
  80 kg m/s done clear
  C)
  8 kg m/s done clear
  D)
  40 kg m/s done clear
  View Solution play_arrow

• question_answer8)
  The unit of measuring momentum of moving body is
  A)
  \[{{\operatorname{ms}}^{-1}}\]                    done clear
  B)
  kg-\[{{\operatorname{ms}}^{-1}}\] done clear
  C)
  kg-\[{{\operatorname{ms}}^{-2}}\]                    done clear
  D)
  \[N-{{m}^{2}}k{{g}^{-2}}\] done clear
  View Solution play_arrow

• question_answer9)
  If the mass of a body and the force acting on it are both doubled, what happens to the acceleration?
  A)
  doubled                                     done clear
  B)
  halved done clear
  C)
  remains same                             done clear
  D)
  becomes zero done clear
  View Solution play_arrow

• question_answer10)
  If the force acting on the body is zero, its momentum will be
  A)
  zero                                           done clear
  B)
  constant done clear
  C)
  infinite                                       done clear
  D)
  variable done clear
  View Solution play_arrow

• question_answer11)

  Read the following and answer any four questions from [11] to [15].

  A car was travelling at 30 m/s. The driver applies brakes suddenly by seeing a running dog. The velocity-time (v-t) graph and its corresponding table during the time of applying brakes is shown below.

  Velocity-time graph shows how the velocity of a body changes with passage of time. To draw velocity-time graph, velocity of the body is plotted along V-axis and the time taken by the body is plotted along X-axis.

  The area under velocity-time graph gives displacement.

  Time Velocity 0 (s) 30 m/s 1 (s) 23.5 m/s 2 (s) 17 m/s 3 (s) 11 m/s 4(s) 5 m/s 4.8(s) 0

  The rate at which the velocity of a car decreases (deceleration) is
  A)
  2.25\[{{\operatorname{ms}}^{-2}}\]                  done clear
  B)
  6.25\[{{\operatorname{ms}}^{-2}}\] done clear
  C)
  7\[{{\operatorname{ms}}^{-2}}\]                      done clear
  D)
  7.85\[{{\operatorname{ms}}^{-2}}\] done clear
  View Solution play_arrow

• question_answer12)
  What is the magnitude of braking force, if the mass of the car is 900 kg?
  A)
  5625 N                                      done clear
  B)
  6625 N done clear
  C)
  7025 N                                      done clear
  D)
  7625 N done clear
  View Solution play_arrow

• question_answer13)
  Calculate the braking distance travelled by the car.
  A)
  36 m                                         done clear
  B)
  60 m done clear
  C)
  72 m                                         done clear
  D)
  86 m done clear
  View Solution play_arrow

• question_answer14)
  A constant force (F) is applied on a stationary particle of mass (m). The velocity attained by the particle after a certain displacement will be proportional to
  A)
  \[\frac{1}{\sqrt{m}}\]                 done clear
  B)
  m done clear
  C)
  \[\frac{1}{m}\]                          done clear
  D)
  \[\sqrt{m}\] done clear
  View Solution play_arrow

• question_answer15)
  The same net force is applied to object A and B. The observed accelerations of the two objects are not the same; object A has an acceleration three times that of object B. Which of the following is correct?
  A)
  Object A has three times the mass of object B. done clear
  B)
  Object A has one-third mass of object B. done clear
  C)
  Object A has a different, less streamlined shape than object B. done clear
  D)
  Object A has more friction than object B. done clear
  View Solution play_arrow

• question_answer16)

  Read the following and answer any four questions from [16] to [20].

  Newton studied the ideas of Galileo regarding the motion of an object. He formulated three fundamental laws that govern the motion of objects. These three laws are known as Newton’s laws of motion.

  The first law of motion states that an object will continue to remain in its state of rest or of uniform motion along a straight line path unless an external force acts on it. This means, all objects resist change in their state.

  The second law of motion states that the rate of change of momentum of an object is directly proportional to the applied external force and takes place in the direction in which external force acts.

  The third law of motion states that whenever an object exerts a force on another object, then the second object exerts an equal and opposite force on the first object.

  A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to

  I. exert larger force on the ball

  II. reduce the force exerted by the ball on hands

  III. increase the rate of change of momentum

  IV. decrease the rate of change of momentum

  A)
  I, II                                           done clear
  B)
  II, IV done clear
  C)
  II, III                                         done clear
  D)
  I, IV done clear
  View Solution play_arrow

• question_answer17)

  According to the third law of motion, action and reaction

  P. always exist in pair.

  Q. always act on different bodies in opposite directions.

  R. have same magnitude and direction

  S. act on either body at normal to each other

  A)
  P                                              done clear
  B)
  P, R     done clear
  C)
  P, Q                                          done clear
  D)
  S done clear
  View Solution play_arrow

• question_answer18)

  The given graph represents

  A)
  the velocity of the body is variable done clear
  B)
  the velocity of the body is constant done clear
  C)
  the mass of the body is constant done clear
  D)
  None of the above done clear
  View Solution play_arrow

• question_answer19)

  Velocity-time graph of a moving particle of mass 1 kg is shown below. The force acting on the particle is

  A)
  0                                              done clear
  B)
  4 N done clear
  C)
  8 N                                           done clear
  D)
  10 N done clear
  View Solution play_arrow

• question_answer20)
  How much momentum will a dumb bell of mass 10 kg transfer to the floor, if it falls from a height of 80 cm ? [Take, its downward acceleration to be \[10c{{m}^{-2}}\] ]
  A)
  10kg-\[{{\operatorname{ms}}^{-1}}\]    done clear
  B)
  20kg-\[{{\operatorname{ms}}^{-1}}\] done clear
  C)
  3ukg-\[{{\operatorname{ms}}^{-1}}\]    done clear
  D)
  40kg-\[{{\operatorname{ms}}^{-1}}\] done clear
  View Solution play_arrow

• question_answer21)

  Read the following and answer any four questions from [21] to [25].

  A rocket is used for carrying a satellite, etc to a suitable height above the ground. Thrust is generated by the propulsion system of the aircraft. For every action there is an equal and opposite reaction.

  The fuel in the rocket is burnt and exhaust gases are made to escape in the downward direction through a narrow nozzle.

  As a reaction, rocket moves upwards. Rocket works on the principle of conservation of momentum.

  According to the principle of conservation of linear momentum, the linear momentum of mass of rocket at any instant must be equal to vector sum of linear momentum of rocket and linear momentum of exhaust gases as the exhaust gases escape.

  The residual mass of rocket decreases with time. Motion of rocket is an accelerated motion.

  How is mass of rocket related to the mass of gases it expels?
  A)
  Mass of rocket is greater than mass of gases it expels. done clear
  B)
  Mass of rocket is less than mass of gases it expels. done clear
  C)
  Mass of rocket is equal to mass of gases it expels. done clear
  D)
  Mass of rocket is not related to the mass of gases it expels. done clear
  View Solution play_arrow

• question_answer22)
  The fuel in the rocket is burnt and exhaust gases are made to escape in
  A)
  parallel to rocket                         done clear
  B)
  upward direction done clear
  C)
  perpendicular to rocket                 done clear
  D)
  downward direction done clear
  View Solution play_arrow

• question_answer23)
  The statement "For every action there is an equal and opposite reaction", is related to which of the following?
  A)
  Newton's first law done clear
  B)
  Newton's second law done clear
  C)
  Newton's third law done clear
  D)
  Law of conservation of momentum done clear
  View Solution play_arrow

• question_answer24)
  What type of motion is described by the rocket?
  A)
  Uniform,                                    done clear
  B)
  Accelerated done clear
  C)
  Both [a] and [b]                          done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer25)
  A horse pulling a tanga moves forward due to the force exerted by
  A)
  The horse on the ground with his feet done clear
  B)
  The horse on the tanga done clear
  C)
  The ground on the horse's feet done clear
  D)
  The tanga on the horse done clear
  View Solution play_arrow