‌sinbt) .......(i) where, A and B are constants. As we know that, F=
dp
dt
From Eq. (i), we get ⇒F=
d
dt
(A
^
i
‌cos‌b‌t−A
^
j
‌sin‌b‌t) ⇒F=−A
^
i
b‌sin‌b‌t−A
^
j
b‌cos‌b‌t Now, dot product =F.p =(−A
^
i
b‌sin‌b‌t−A
^
j
b‌cos‌b‌t).(A
^
i
‌cos‌b‌t−A
^
j
‌sin‌b‌t) =−Ab‌sin‌b‌t‌cos‌b‌t+Ab‌sin‌b‌t‌cos‌b‌t =0 Since, F.p=Fp‌cos‌θ=0 ⇒cos‌θ=0⇒θ=90° Hence, the angle between momentum p and force F is 90°.