Physics motion Q (20)

Velocity is a vector quantity. It has magnitude and direction.

Speed is a scalar quantity. It has magnitude only.

1)
Uniform motion means "moving with constant velocity (=constant speed along a straight line)

2)
If the speed of an object keeps constant but with changing direction (e.g. bending around a corner.), since its direction is changing, its velocity is changing. This is an example of non-uniform motion.

3)
If the velocity of an object remains constant, then its magnitude and direction are kept unchanged. Thus, its speed MUST remains unchanged.

4)
Of course.
Just like an object is projected upwards. Although it is moving upwards (have a upwards velocity), but its acceleration is pointing downwards (because it is due to gravity). So we observe the rising object "decelerating".
This means deceleration = acceleration in the opposite direction.
Thus, an object can have a northward velocity (moving towards North) with deceleration (acceleration in the opposite direction, i.e. southward direction).

1) (Does it require daily-life examples?)
Uniform motion: a motion in which the velocity remains constant, both of its direction and magnitude remain unchanged. [In other words, an object moves in one direction along a straight with a constant speed.] Also, the acceleration is always zero.
e.g. a train moving forwards on a rail with its speed being kept constant
Non-uniform motion: a motion in which the velocity varies, either its direction or magnitude (or both) changes over time. Also, the acceleration is non-zero.
e.g. the Earth orbiting around the Sun/ the motion of a ball when released from the top of a tower

2) Yes. Consider a uniform circular motion. The linear speed of a particle remains constant while the direction of motion, and hence the velocity, is changing, since there is always an acceleration pointing towards the centre of the circle. [Note: the linear speed (or the magnitude of the velocity) does not change because the centripetal force/acceleration is always perpendicular to the direction of the velocity, therefore, there is no work done to the particle.]

3) No. If the instantaneous velocity remains constant, its magnitude (which is its speed) must also remains constant.

4) Yes. The direction of acceleration has nothing to do with the direction of velocity, it depends on the direction of the net force acting on the object. Therefore, it is possible for an object travelling to the north (having a northward velocity) to experience a net force pointing to the south (having a southward acceleration).