You push downward on a trunk at an angle 25° below the horizontal with a force of 750 n. if the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move?

N = normal force on the trunk

m = mass of the trunk

W = weight of the trunk = mg

Using equilibrium of force in vertical direction

N = W + 750 Sin25

N = mg + 750 Sin25                                       eq-1

μ = Coefficient of static friction = 0.61

f = static frictional force

static frictional force is given as

f = μN

using eq-1

f = (0.61) (mg + 750 Sin25)                           eq-2

Along the horizontal direction , for the trunk to move, force equation must be

750 Cos25 = f

using eq-2

750 Cos25 = (0.61) (mg + 750 Sin25)

750 Cos25 = (0.61) (m (9.8) + 750 Sin25)

m = 81.4 kg