Question

An object with a mass of 1.25 kg is initially at rest. There is a net force acting on the object F(t) = [25.0N – (6.00 N/s2)t?]î. This object will start moving to the right, and after a while it will move to the left. What is the speed of the object when it passes its original position moving to the left?

Answer 1

Force on the object is

F=m* = (25 – 6t?)

= - = (20 - 4.8+)

dū = (20 – 4.8t)dt i

[* dv = [ (20 – 4.8i)dit Jo

v = (20t – 1.6ť)

= (20t – 1.663)

dx = (20t – 1.6tdt

ſ dx = [ (201 – 1.6c* ydt JO

r = (102 - 0.4++)

When the object returns to its original position, $x=0$ ,

(10+ - 0.4) = 0 =t=0s or t = 5s

That is the object returns to its original position at time

t=5

Velocity of object at that time is

v = (20t – 1.6ť) = 20*5 – 1.6 * 53 = -100 m/s

Speed of object when it passes its original position is

u = 100 m/s