Question

explain whether or not a particle would have acceleration if (a) it's moving in a straight line with constant speed, and (b) moving around a curve with constant speed

Answer 1

What does it mean for something to accelerate? What has to change?

Answer 2

velocity ?

Answer 3

Correct.

And in which of the 2 cases does the velocity change? (Remember that velocity is a vector quantity meaning you have to take into account the speed _and_ the direction)

Answer 4

if it is moving on astright line it has no acc for constant speed
if along a curve then it has centripetal acceleration toward the centre of curve

Answer 5

the velocity changes in the second case

Answer 6

yes it changes but not he magnitude but its direction
and since it is a vector quantity so if direction changes evevn if magnitude is constant then also it changes

Answer 7

so the direction changes, but magnitude doesn't? therefore, since direction changes, there's also a change in acceleration?

Answer 8

yes definitly

Answer 9

okay, thank you!

Answer 10

Acceleration is the rate of change of velocity.

In (a), it is possible there is an acceleration if
the object suddenly moves in the opposite direction
in a small time of t;
i.e. a = 2*v/t

In (b), for the object to move in a curve,
the direction of its motion must be changing all the time, and
thus its velocity changes,
leading to non-zero acceleration.