An object moving a 30 m/s to the right begins to accelerate at 5 m/s^2 to the left for 3 seconds.?

Then the question is. What is (a) the displacement and (b) the velocity of the object after 3 seconds? (Include direction in your answer.)





I need help on this physics question because my physics teacher isn't really good at teaching us haha. Well please help and thank you.An object moving a 30 m/s to the right begins to accelerate at 5 m/s^2 to the left for 3 seconds.?
If your object is moving to the right and it undergoes an acceleration to the left, this is a negative acceleration - the car is slowing down. Using basic motion equations we can solve this problem. Let's identify what variables we need that the question gives us:





Acceleration = - 5 m/s^2


Time = 3 s


Initial velocity = 30 m/s [right]


Final velocity = ?


Displacement = ?





For a), we need to solve for displacement.


Displacement = (initial velocity)(time) + 0.5(acceleration)(time)^2


= (30 m/s [right])(3 s) + 0.5(- 5 m/s^2[right])(3 s)^2


= 90 m [right] + (-22.5 [right])


= 67.5 m





For b), we need to solve for the final velocity after it has travelled this far.





final velocity^2 = (initial velocity)^2 + 2(acceleration)(displacement)


= SQRT (30 m/s [right])^2 + 2(- 5 m/s^2[right])(67.5 m)


= SQRT (900 m/s [right] + (- 337.5 m/s [right])


= SQRT 562.5 m/s [right]


final velocity = 23.72 m/s [right]





The SQRT mean you must take the square root of whatever your answer in brackets is since the variable we are solving for is squared.


These equations are given to you in grade 11 I believe - it's best to memorize 'em!