# Why is it impossible to start or stop an object instantaneously? In what ways can a non-accelerating object move? [closed]

Why is it impossible to start or stop an object instantaneously? In what ways can a non-accelerating object move?

I think this has to do something with inertia, but I am not exactly sure I fully understand the concept.

For the second part, does this mean, like a book sitting on a table, but the world is still spinning, therefore, the book is changing direction and is then accelerating?

Any help would be appreciated!

• Hint for question 1: how much acceleration would it take to instantaneously change the velocity of an object by a finite amount? Hint for question 2: acceleration is change in velocity. Consider the implications of acceleration being zero. – probably_someone Oct 7 '19 at 0:12
• Define "instantaneously". And note - an electron exposed to an electric field accelerates at an EXTREME rate due to its very small mass and large charge/mass ratio. – David White Oct 7 '19 at 1:55

To move an object you must apply a force where $$F = m\vec a\ and\ \vec a = d\vec v/dt$$. To move it instantaneously implies that dt --> 0 and the force would go to infinity. Hence instantaneous acceleration or deceleration is impossible.