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Lab 10: Moment of Inertia Lab 10: Moment of Inertia Objective: We will test Newt

ID: 3281413 • Letter: L

Question

Lab 10: Moment of Inertia Lab 10: Moment of Inertia Objective: We will test Newton's Laws for Rotation to measure the moment of inertia of a disk. First, we obtain the moment of inertia of a disk simply by measuring its mass and its radius and compute its moment of inertia easily from these quantities. This will be the theoretical value of the moment of inertia of the main disk. Next, we obtain the moment of inertia of a disk applying Newton's Laws of Rotation. If Newton's Laws of rotation are experimentally valid, then any moment of inertia calculated by using them should match the moment of inertia we measured previously Materials: Rotational Motion Apparatus Meter Stick .Hooked Mass Set . Stopwatch Computer with Graphing Capability -Axes of Rotation Big RDisk Massless Pulley Direction of Rotation 500 g Figure 10.1: Rotational Motion Diagram 59

Explanation / Answer

17. we know that radius of small hub, r = 0.033 m

for m = 0.25 kg

t = 4s

so linear acceleration of mass = a

a = 2d/t^2 = 2*0.7/4^2 = 0.0875 m/s/s

tension in string = T

T = m(g - a) = 2.430625 N

torque, T' = T*r = 0.08021 Nm

moment of inertia I = 0.167 + 5.446*10^-6 = 0.167005446 kg m^2

hence

angular acceleration = alpha = T/I = 0.4802837 rad/s/s

for m = 0.500 kg

t = 3s

so linear acceleration of mass = a

a = 2d/t^2 = 2*0.7/3^2 = 0.1555 m/s/s

tension in string = T

T = m(g - a) = 4.827 N

torque, T' = T*r = 0.1592 Nm

moment of inertia I = 0.167 + 5.446*10^-6 = 0.167005446 kg m^2

hence

angular acceleration = alpha = T/I = 0.95385 rad/s/s

for m = 0.5 kg

t = 2s

so linear acceleration of mass = a

a = 2d/t^2 = 2*0.7/2^2 = 0.35 m/s/s

tension in string = T

T = m(g - a) = 9.46 N

torque, T' = T*r = 0.2838 Nm

moment of inertia I = 0.167 + 5.446*10^-6 = 0.167005446 kg m^2

hence

angular acceleration = alpha = T/I = 1.6994 rad/s/s