Question

Workers have loaded a delivery truck in such a way that its center of gravity is only slightly forward of the rear axle, as shown in the figure. The mass of the truck and its contents is 6960 kg. Find the magnitudes of the forces exerted by the ground on (a) the front wheels and (b) the rear wheels of the truck.

Answer 1

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Mass of the truck, M = 6960 kg

Distance from the center of gravity to the rear wheel = 0.63 m

Distance from the center of gravity to the front wheel = 2.30 m

Let the force exerted by the ground on the front wheel be F_f and

on the rear wheel be F_r

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Since, the system is in equilibrium the net torque and net forces acting

on the system is zero

The net force acting on the tuck are

         ΣF_y = 0

   F_f + F_r = Mg

                = 6960x9.8 N                                            ...... (1)

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a) Taking the axis of rotation about the center of gravity, and the net

    torque acting on the truck is,

                                     Στ = 0

                     F_r (0.63 m) = F_f (2.30 m)

                                    F_r = 3.65 F_{f ..............(2)}

from equation 1 and 2

                                    F_f = 14665.88 N

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b)Force exerted by the ground on the rear wheel is calculated using

equation (1),

                         F_f + F_r = 6960x9.8 N

                                  F_r = 53542.12 N

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