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Short Answer

Question: Figure P10.41 shows a side view of a car tire before itis mounted on a wheel. Model it as having two side-walls of uniform thickness 0.635 cm and a tread wall of uniform thickness 2.50 cm and width 20.0 cm. Assume the rubber has uniform density 1.10 3 103 kg/m3. Find its moment of inertia about an axis perpendicular to the page through its center.

Itotal=1.28kg·m2

See the step by step solution

Step by Step Solution

Step 1: Definition of moment of inertia

Moment of inertia about a given axis of rotation resists a change in its rotational motion; it can be regarded as a measure of rotational inertia of the body.

Step 2: Finding the wire consists of three parts

1-Two side walls which are modeled as hollow cylinder with inner radius Rs1=16.5cm and outer radius Rs2=30.5cm and thickness tr=2.5cm

2-Tread wall which is modeled as hollow cylinder of inner radius Rt1=30.5cm outer radius localid="1663670015744" (Rt2=33cm) width (w=20cm) and thickness tr=2.5cm.

Step: 3 Calculations for the side wall

First: The moment of inertia of the side wall is

Is=12msRs2+Rs1 → (1)

The mass of the side wall ms is found by

ms=ρVs=ρπRs22-Rs12t

Substituting the numerical values, we get

ms=π1.1×1030.3052-0.16520.635×10-2=1.44kg → (2)

Substituting for from Equation (2) into Equation (1) and substituting numerical values, we get

Is=12(1.44)0.1652+0.3052=8.68×10-2kg·m2

Step: 4 Calculation for the tread wall.

Second: The moment of inertia of the tread wall is

It=12mtRt22+Rt12 → (3)

The mass of the tread wall mt is found by

mt=ρVs=ρπRt22-Rt12tr

Substituting the numerical values, we get

mt=π1.1×1030.332-0.305220×10-2=11kg → (4)

Substituting for from Equation (4) into Equation (3) and substituting numerical values, we get

It=12(11)0.332+0.3052=1.11kg·m2

Step: 5 Calculating inertia for the entire tire.

Hence, the total inertia for the entire tire is

Itotal=2Is+It

Substituting the numerical values, we get

Itotal=28.68×10-2+1.11

=1.28kg·m2

The solution is Itotal=1.28kg·m2.

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