A team of eight dogs pulls a sled with waxed wood runners on wet snow (mush!). The dogs have average masses of 19.0 kg, and the loaded sled with its rider has a mass of 210 kg. (a) Calculate the magnitude of the acceleration starting from rest if each dog exerts an average force of 185 N backward on the snow. (b) What is the magnitude of the acceleration once the sled starts to move? (c) For both situations, calculate the magnitude of the force in the coupling between the dogs and the sled.

a.)

Step 1 of

The magnitude of acceleration (a) starting from rest can be calculated by drawing the free body diagram for the problem and solving the force equation.

The equation for force is,

Where, F = Force exerted by eight dogs in N

f = frictional force in N

M = The total mass of 8 dogs and sled with rider in kg

Step 2 of

The Force (F) exerted by eight dogs is,

Where, Favg= average force exerted by each dog

Substituting 210 kg for Favg

= 1480 N

Step 3 of

The total mass(M) of 8 dogs and sled with rider is,

where, md= average mass of a dog in kg

ms= mass of the sled with rider in kg

Substituting 19 kg md and 210 kg for ms

= 152+210

= 362 kg

Step 4 of

Since we are calculating the acceleration starting from rest, static friction is acting between the sled (waxed wood) and wet snow. The static frictional force f is given by,

Where, s= coefficient of static friction between

waxed wood and wet snow

m = mass of the sled with rider in kg

g = acceleration due to gravity in ms2

Substituting 0.14 for S, 210 kg for m, 9.8 m/s2 for g

= 288.12 N