Question

"the acceleration is taken to be positive if it's in the direction of velocity, and negative when it is opposite to the direction of velocity" what does this mean in simple words? I can't understand what they want to say by saying direction of velocity ​

Answer 1

see, when the speed of the object increases, the velocity also increases. and an increasing velocity is considered to be positive (as more speed is adding up).

whereas when the direction changes, i.e. the object's speed decreases, the velocity also decreases. and a decreasing velocity is considered to be negative (as speed is getting subtracted)

this is what's explained just that speed here means acceleration but to make u understand I hv used easier language.

hope this helps you...