## MCQs on Dynamics, Grade 9

- A 30 kg object is support from rope such that tension in the rope is equal to its weight. The weight of the object is

A. 30 kg | B. 30 N | C. | D. 9.8 N/kg |

- Force needed to produce an acceleration of 10 ms
^{-2}in a ball of mass 0.5 kg is

A. 20 N | B. 10.5 N | C. 9.5 N | D. |

- Ball A collides with ball B which is at rest. After the collision which of the following condition is not possible

A. Ball A comes to rest and ball B starts moving | B. Both balls move in same direction | C. both balls move in opposite directions | D. |

- What is the mass of a car that is travelling with a velocity of 20 m/s [W] and a momentum of 22000 kg m/s [W]

A. 440000 kg | B. 21980 kg | C. 22020 kg | D. |

- An object at earth and taken to should have

A. less mass/less weight | B. same/more weight | C. | D. less mass/same weight |

- The unit of coefficient of friction is

A. N | B. kg | C. μ | D. |

- The centripetal acceleration of an object of mass 1 kg moving with 6 m/s in a circle of radius 3 m is

A. 18 ms | B. | C. 10 ms | D. 2 ms |

- How many times the centripetal force will increase if the mass of a body moving with uniform speed in a circle is doubled.

10.

A. Six times | B. | C. Four times | D. Eight times |

- Which of the following forces can act as centripetal forces

A. tension | B. friction | C. gravitational force | D. |

- An empty suitcase is placed in the middle of a bus on its floor traveling at high speed. When the bus brakes suddenly, the suitcase slides

A. backwards | B. | C. jumps up | D. remains in place |

- In Newton’s third law the action reaction pair does not neutralize each other, because they

A. act on same body | B. | C. act on third body | D. produce friction |