Answer:
78.6 N
Explanation:
Considering the change in kinetic energy is equal to force*time then knowing that kinetic energy change is given by
[tex]\triangle KE= 0.5m(v_f^{2}-v_i^{2})=ft[/tex] where m is the mass, v is velocity, subscripts f and i for final and initial respectively, f for force and t is time
[tex]\triangle KE=0.5*1.5(7.7^{2}-8.9^{2})=0.19f\\F\approx 78.6N [/tex]
