CBSE  /  Class 9  /  Science  /  Force and Laws of Motion

  • 1. 
    Which of the following statements is not correct for an object moving along a straight path in an accelerated motion?

  • Its speed keeps changing
  • Its velocity always changes
  • It always goes away from the Earth
  • A force is always acting on it

  • 2. 
    According to the third law of motion, action and reaction

  • 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

  • 3. 
    A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to

  • exert larger force on the ball
  • reduce the force exerted by the balls on the hands
  • increase the rate of change of momentum
  • decrease the rate of change of momentum

  • 4. 
    The inertia of an object tends to cause the object

  • to increase its speed
  • to decrease its speed
  • to resist any change in its state of motion
  • to decelerate due to friction

  • 5. 
    A passenger in a moving train tosses a coin which falls behind him. It means that motion of the train is

  • accelerated
  • uniform
  • retarded
  • along circular tracks

  • 6. 
    An object of mass 2 kg is sliding with a constant velocity of 4 ms

  • 32 N
  • 0 N
  • 2 N
  • 8 N

  • 7. 
    From newton’s Ist law of motion, since there is no external force acting on the object it will remain in its original state of motion. Hence, zero force is required to keep the object moving with constant velocity, correct answer is B. Rocket works on the principle of conservation of

  • mass
  • energy
  • momentum
  • velocity

  • 8. 
    A water tanker filled up to \(\frac{2}{3}\) of its height is moving with a uniform speed. On a sudden application of brakes, the water in the tank would

  • move backward
  • move forward
  • be unaffected
  • rise upwards

  • 9. 
    If the mass of a body is doubled and its velocity becomes half, then the linear momentum of the body will

  • remain same
  • become double
  • become half
  • become four times.

  • 10. 
    When a number of forces acting simultaneously on a body bring about a change in its state of rest or of uniform motion in a straight line, then these forces acting on the body are said to be

  • balanced forces
  • equal forces
  • unbalanced forces
  • opposite forces
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