Question

Consider a vehicle going on a horizontal road towards east. Neglect any force by the air. The frictional forces on the vehicle by the road

• A. Is towards east if the vehicle is accelerating
• B. Is zero if the vehicle is moving with a uniform velocity
• C. Must be towards east
• D. Must be towards west

Answer 1

Answer: (A), (B)

The correct options are
A

Is towards east if the vehicle is accelerating

B

Is zero if the vehicle is moving with a uniform velocity

Option (a) says friction force will be in east if car is accelerating.

Well car is going in east direction and if it is accelerating then the net force has to be in east direction. Well there can be no other force than frictional force in horizontal direction. so option (a) is correct.

Option (b) says force is 0 if constant velocity which means 0 acceleration

$\Rightarrow$ 0 net external force so no friction possible as again friction can be the only external force on the body along horizontal line.

Option (c) Must be towards east

Must

Pretty strong word

Well if the acceleration was in east direction then the option would have been correct but since nothing mentioned about it so we can't talk about Net force or its direction

Option (d) same as above both C & D are wrong