## MCQs on Dynamics, Grade 9

1. 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. 294 N D. 9.8 N/kg

1. 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. 5 N

1. 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. both balls are at rest

1. 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. 1100 kg

1. An object at earth and taken to should have
 A. less mass/less weight B. same/more weight C. same mass/less weight D. less mass/same weight

1. The unit of coefficient of friction is
 A. N B. kg C. μ D. It has no units

1. 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-2 B. 12 ms-2 C. 10 ms-2 D. 2 ms-2

1. 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. Two times C. Four times D. Eight times

1. Which of the following forces can act as centripetal forces
 A. tension B. friction C. gravitational force D. All of these

1. 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. forward C. jumps up D. remains in place

1. In Newton’s third law the action reaction pair does not neutralize each other, because they
 A. act on same body B. act on different bodies C. act on third body D. produce friction