Explanation:
Let [tex]F[/tex] be the force exerted by the student.
Let [tex]F_{v}[/tex] be the vertical component of force.
Let [tex]\alpha[/tex] be the angle between horizontal and direction of application of force.
Given,
[tex]F=50N\\\alpha =45^{0}[/tex]
[tex]F_{h}=Fcos\alpha =50\times cos45=35.35N\\[/tex]
Let [tex]w[/tex] be the weight of the object.
Given mass of box=[tex]m=20Kg[/tex]
[tex]w=mg=20\times 9.8=196N[/tex]
Let [tex]N[/tex] be the normal force.
Since the vertical force from student is in opposite direction of that of weight of box,
[tex]N=mg-F_{v}[/tex]
[tex]N=196-35.35\\N=160.65Newtons[/tex]
