Question

. A tire typically has a coefficient of friction around 0.7 in dry conditions. In wet

conditions, the coefficient of friction drops to around 0.4. What is the difference
between the frictional force in dry conditions compared to wet conditions on a car
that has a weight of 14000 N.

Answer 1

4300N

Step-by-step explanation:

Friction

Based on the free body diagram, the friction (fFr in the attached diagram) is dependent on the reaction force (Rn in the attached diagram) acting on the object, in this case a car. The frictional force will always act against the direction of movement (DOM in the attached diagram.)

Solution

Given the condition is dry,

Summation of forces in the vertical direction (Positive for upward forces) = 0

Reaction Force - Weight of car = 0

Reaction Force = Weight of car = 14000N

Since the friction is dependent on the reaction force with the formula: Coefficient of friction X Reaction Force,

Friction (Dry Condition) = 0.7 * 14000N = 9800N

Now given the condition is wet,

We will use the same formula but with a change to the coefficient of friction.

Friction (Wet Condition) = 0.4 * 14000N = 5600N

Difference between them = 9800N - 5600N = 4300N.