A child attempts to roll a ball up a long ramp and it slows as it goes up. If it is released at 2.5 m/s upward and accelerates downward at 0.8 m/s2, how fast is the ball moving after 4 seconds?

-0.7 m/s

Explanation:

Initial velocity (u)= 2.5 m/s

Acceleleration (a)= -0.8 m/s^2

Time taken (t) = 4  seconds

Hence,

v=u+at [1st Equation of motion]

v=2.5+-0.8*4

v=2.5-3.2

v=-0.7 m/s

Note that the negative sign indicates that the ball has changed direction and rolls downwards with gravity

scientific laws are the result of testing theories and proving them to be facts.