Question

15. A body of mass 5kg starts from the origin
with an initial velocity u = 30î +40 jms.
If a constant force F =-(+5j)N acts on
the body, the time in which the y - compo-
nent of the velocity becomes zero is
2) 20s 3) 40s 4) 80s
21
1) 55​

Answer 1

Answer

Here, mass of the body , m=5kg; y-component of initial velocity, uy=40m/s and y-component of the force, Fy=−5N

Using F=ma,  ay=mFy=5−5=−1 m/s2 

Using formula, v=u+at

vy=uy+ayt

So, 0=40−t

∴t=40 sec