Question 6
At a certain moment the velocity of an object moving along a straight path was 2 m s-1. It was then subjected to a uniform acceleration for 4 s, which changed the velocity to 6 m s-1. What was the object's acceleration during those 4 seconds?
The right answer is the one marked above.
1 m s-2. The initial velocity is not zero, so the change in velocity has to be found first:
acceleration = (6 − 2) m s-1 ÷ 4 s = 4 ÷ 4 = 1 m s-2
The velocity therefore rises by 1 m s-1 each second: 2, 3, 4, 5, 6. Dividing only the final velocity of 6 by the time gives 1.5, which is wrong — subtracting the initial velocity is the step not to forget.