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A hoop of radius 0.53m and mass 3.00kg rolls down a ramp of length 4.5m that makes an angle of 25° with the horizontal. The hoop starts from rest from the top of the ramp. Find the angular speed of the hoop at the bottom of the ramp.

User SMSidat
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2 Answers

2 votes

Final answer:

Using the conservation of mechanical energy principle in Physics, the student can determine the angular speed of the hoop at the bottom of the ramp after calculating the vertical drop height from the ramp length and angle.

Step-by-step explanation:

A problem in classical mechanics, specifically involving rotational motion and energy conservation principles applicable in Physics. To find the angular speed of the hoop at the bottom of the ramp, the conservation of mechanical energy can be utilized. The gravitational potential energy at the top of the ramp is entirely converted into translational and rotational kinetic energy at the bottom because there is no slipping. The moment of inertia for a hoop is \(I = mr^2\) where \(m\) is the mass and \(r\) is the radius of the hoop. Using the conservation of energy:

\(mgh = \frac{1}{2}mv^2 + \frac{1}{2}I\omega^2\)

Since \(v = \omega r\) (for rolling without slipping) and \(I = mr^2\), all terms containing mass can be canceled out:

\(gh = \frac{1}{2}v^2 + \frac{1}{2}v^2\)

Thus, \(v^2 = \frac{2gh}{2} = gh\) and \(v = \sqrt{gh}\).

With \(h\) being the vertical drop which can be calculated by \(h = L \sin(\theta)\), where \(L\) is the length of the ramp and \(\theta\) is the incline angle, we can find \(v\) and subsequently the final angular speed \(\omega\).

The substitution gives:

\(h = 4.5m \sin(25^\circ)\)

\(v = \sqrt{9.8 \frac{m}{s^2} \times h}\)

Finally, \(\omega = \frac{v}{r}\) where \(r\) is the radius of the hoop, which completes the solution.

User Eyelash
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3 votes

Final answer:

The angular speed of the hoop at the bottom of the ramp is 5.84 rad/s.

Step-by-step explanation:

To find the angular speed of the hoop at the bottom of the ramp, we can use the principle of conservation of energy. The potential energy at the top of the ramp is converted into kinetic energy at the bottom of the ramp.

We start by calculating the potential energy at the top of the ramp using the formula PE = mgh, where m is the mass of the hoop, g is the acceleration due to gravity, and h is the vertical height of the ramp.

Then, we can use the equation for the kinetic energy of a rotating object, KE = (1/2)Iω², where I is the moment of inertia and ω is the angular speed, to find the angular speed at the bottom of the ramp.

Substituting the given values, we have PE = (3.00 kg)(9.8 m/s²)(4.5 m) and KE = (1/2)(0.5MR²)(ω²), where M is the mass of the hoop, R is the radius of the hoop, and ω is the angular speed. Equating the potential energy and kinetic energy, we can solve for ω.

ω =
\sqrt{(2gh/R^2)

ω
= √((2(9.8 m/s^2)(4.5 m)/(0.53 m)^2)) = 5.84 rad/s

User Danielpiestrak
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