An object of $m\, kg$ with speed of $v\, m/s$ strikes a wall at an angle $\theta$ and rebounds at the same speed and same angle. The magnitude of the change in momentum of the object will be
$2m\,v\,\cos \theta $
$2\,m\,v\,\sin \theta $
$0$
$2\,m\,v$
An object of $m\, kg$ with speed of $v\, m/s$ strikes a wall at an angle $\theta$ and rebounds at the same speed and same angle. The magnitude of the change in momentum of the object will be
${\overrightarrow P _1} = m\,v\,\sin \theta \,\hat i - m\,v\,\cos \theta \,\hat j$
and ${\overrightarrow P _2} = m\,v\,\sin \theta \,\hat i + \,m\,v\,\cos \theta \,\hat j$
So change in momentum
$\overrightarrow {\Delta P} = {\overrightarrow P _2} - {\overrightarrow P _1} = 2\,m\,v\,\cos \theta \,\hat j,$$|\Delta \overrightarrow P |\, = 2\,m\,v\,\cos \theta $
and ${\overrightarrow P _2} = m\,v\,\sin \theta \,\hat i + \,m\,v\,\cos \theta \,\hat j$
So change in momentum
$\overrightarrow {\Delta P} = {\overrightarrow P _2} - {\overrightarrow P _1} = 2\,m\,v\,\cos \theta \,\hat j,$$|\Delta \overrightarrow P |\, = 2\,m\,v\,\cos \theta $