As per Newton's law we have
[tex]F_{net} = ma[/tex]
here for the mass suspended with a string we have
[tex]F_{net} = T - mg[/tex]
now we have
[tex]T - mg = ma[/tex]
[tex]T = mg + ma[/tex]
[tex]T = 5(9.8) + 5(1.5)[/tex]
[tex]T = 56.5 N[/tex]
so the tension in the string will be 56.5 N