Question

Which of Shakina's statements regarding acceleration and velocity is false?
1- "When the acceleration is negative, the velocity can be either negative or positive."

2- "When the acceleration and velocity are in opposite directions, the particle slows down."

3- "When the acceleration is negative, the velocity must also be negative."

4- "When the acceleration and velocity are in the same direction, the particle speeds up."

Answer 1

Suppose we throw a ball vertically upwards with some velocity V.. In this case the acceleration on the ball will be g but in downward direction though the ball will keeping up to a certain height where its velocity will become zero and then it will fall back.

This suggests that whenever the acceleration and velocity are in opposite direction there is a retarding force i.e. the particle slows down. The velocity may be in opposite direction for a while as we have just seen.