Physics Rotational Mechanics Level: High School
Rotational Kinetic Energy
A thin rod of length 0.75 m and mass 0.42 kg is suspended freely form one end . It is pulled to one side and then allowed to swing like a pendulum, passing through its lowest position with angular speed 4.0 rad/s . Neglecting friction and air resistance , finda) The rod’s kinetic energy at is lowest position .
b) How far above that position the center of mass rises .
Physics Rotational Mechanics Level: High School
Moment of Inertia
Figure at “click here” shows an arrangement of 15 identical disk that have been glued together in a rod-like shape of length L = 1.0000 m and (total) mass M = 100.0 mg . the arrangement can rotate about a perpendicular axis through its central disk at point O .a) What is the rotational inertia of the arrangement about that axis ?
b) If we approximated the arrangement as being a uniform rod of mass M and length L , what percentage error would we make in using the formula in table 10-2e to calculate the rotational inertia ?
Physics Rotational Mechanics Level: High School
Circular Motion and Friction
A record turntable is rotating at 33 1/3 rev/min . A watermelon seed is on the turntable 6.0 cm from the axis of rotation .a) Calculate the acceleration of the seed , assuming that it does not slip .
b) What is the minimum value of the coefficient of static friction between the seed and the turntable if the seed is not to slip ?
c) Suppose that the turntable achieves its angular speed by starting from rest and undergoing a constant angular acceleration for 0.25 s. Calculate the minimum coefficient of static friction required for the seed not to slip during the acceleration period .
Physics Rotational Mechanics Level: High School
Rotational Kinetic Energy
Rigid rods of negligible mass lying along the y axis connect three particles (see figure at “click here) . If the system rotates about the x axis with an angular speed of 2.00 rad/s . finda) the moment of inertia about the x axis and the total rotational kinetic energy evaluated from ½ Iw^2 .
b) The tangential speed of each particle and the total kinetic energy evaluated from sigma ½ mivi^2 .
Physics Rotational Mechanics Level: High School
A common demonstration illustrated in the figure at “click here” consists of a ball resting at one end of a uniform board of length l , hinged at the other end , and elevated at an angle theta . A light cup is attached to the board at ‘re’ so that it will catch the ball when the support stick is suddenly removed .a) show that the ball will lag behind the falling board when theta is less than 35.3 degree .
b) If the board is 1.00 m long and is supported at this limiting angle , show that the cup must be 18.4 cm from the moving end .
Physics Rotational Mechanics Level: High School
Rotational Kinetic Energy
The top in the figure at “click here” has a moment of inertia of 4.00 x 10^-4 kg.m^2 and is initially at rest . It is free to rotate about the stationary axis AA’ . A string , wrapped around a peg along the axis of the top , is pulled in such a manner as to maintain a constant tension of 5.57 N . If the string does not slip while it is unwound from the peg , what is the angular speed of the top after 80.0 cm of string has been pulled off the peg ?
Physics Rotational Mechanics Level: High School
A rigid body rotates about a fixed axis with a constant angular acceleration. Which one of the following statements is true concerning the tangential acceleration of any point on the body ?a) Its magnitude is zero m/s^2.
b) It depends on the angular velocity .
c) It is equal to the centripetal acceleration .
d) It is constant in both magnitude and direction .
e) It depends on the change in the angular velocity .
Physics Rotational Mechanics Level: High School
Conservation of Angular Momentum
Danelle is moving in a spaceship at a constant velocity away from a group of stars . What happens when a spinning ice skater draws in her outstretched arms ?a) Her angular momentum decreases .
b) Her angular momentum increases .
c) Her moment of inertia decreases causing her to speed up .
d) Her moment of inertia decreases causing her to slow down .
e) The torque that she exerts increase her moment of inertia .
Physics Rotational Mechanics Level: High School
Rotational Equilibrium
A uniform plank of length 6.80 m and mass 25 kg is resting on two supports , one located at x = 0.0 m and the other located at x = 5.10 m , as shown in the figure at “click here” . A person of unknown mass walks out on the overhang until the plank just begins to tip , at which time the support on the left , ie, the one located at x = 0.0 m , is removed . When this occurs , the person is located at x = 5.78 m , as measured from the x = 0.00 . What is the mass of the person (in kg) ?a) 62.5
b) 90.6
c) 131.4
d) 190.5
e) 376.3
Physics Rotational Mechanics Level: High School
Circular Motion
A 0.68 kg mass is attached to the end of a 0.80 m long string . The mass is whirled in a horizontal circular path . If the maximum tension that the string can withstand is 200 , what is the maximum speed of the mass (in m/s ) if the string is not to break ?a) 6.5
b) 8.7
c) 1.5
d) 15.3
e) 20.4
Physics Rotational Mechanics Level: High School
Conservation
A hoop of radius 0.5 m and a mass of 0.2 kg is released from rest and allowed to roll down an inclined plane . How fast is it moving after dropping from a vertical distance of 3 m ?2.2 m / s
3.8 m / s
7.7 m / s
5.4 m / s
Physics Rotational Mechanics Level: High School
Conservation of Rotational Equilibrium
A force is applied to the end of a 2 ft long uniform board weighing 50 lb , in order to keep it horizontal . while it pushes against a wall at the left . If the angle the force makes with the board is 30 degrees in the direction . What is the magnitude of the force ?100 lb
28.9 lb
57.7 lb
50 lb
Physics Rotational Mechanics Level: High School
Conservation of Angular Momentum
A diver can change her rate of rotation in the air by “lucking” her head in and bending her knees Let’s assume that when she is stretched out straight she is rotating at 1 revolution per second . Now she goes into the “tuck and bend” , effectively shortening the length of her body by half . what will her rate of rotation be now ?4 Hz
5 Hz
Physics Rotational Mechanics Level: High School
Rotational Kinematics
A wheel with a mass of inertia of 8.0 kg-m2 and a rotational kinetic energy of 155 Joules requires what torque to bring it to rest in 4.0 s ?-16 N m
16 N m
- 12 N m
12 N m
Physics Rotational Mechanics Level: High School
A solid ball , solid cylinder and a hollow pipe all have equal masses and radii . All these items are released simultaneously at the top of an inclined plane , which will reach the bottom first ?None of the listed
Solid cylinder
Solid ball
Hollow pipe
