rotational moion
What is the net torque on the bar shown in (Figure 1), about the axis indicated by the dot? Suppose that FFF = 15 NN
11 N*M
A frictionless pulley, which can be modeled as a 0.82 kgkg solid cylinder with a 0.37 mm radius, has a rope going over it, as shown in
13 rad/s^2
The lightweight wheel on a road bike has a moment of inertia of 0.097 kg⋅m2kg⋅m2. A mechanic, checking the alignment of the wheel, gives it a quick spin; it completes 5 rotations in 2.4 s. To bring the wheel to rest, the mechanic gently applies the disk brakes, which squeeze pads against a metal disk connected to the wheel. The pads touch the disk 7.1 cm from the axle, and the wheel slows down and stops in 1.4 ss.
13N
If Luis pulls straight down on the end of a wrench that is tilted θθ = 30∘∘ above the horizontal and is rrr = 33 cmcm long, what force must he apply to exert a torque of -11 N⋅mN⋅m ?
38
A 230 gg , 21-cm-diameter plastic disk is spun on an axle through its center by an electric motor.What torque must the motor supply to take the disk from 0 to 1900 rpm in 5.0 ss ?
5.0×10^−2 N*m
A professor's office door is 0.86 mm wide, 2.0 mm high, and 4.0 cm thick; has a mass of 25 kg ; and pivots on frictionless hinges. A "door closer" is attached to the door and the top of the door frame.When the door is open and at rest, the door closer exerts a torque of 4.6 N⋅mN⋅m . What is the least force that you need to apply to the door to hold it open?
5.3N
What is the net torque about on the bar shown in (Figure 1) about the axis indicated by the dot? Suppose that ϕϕphi = 50 ∘∘ and θθtheta = 80 ∘
5.9 N*M
The two ends of the barbell shown in (Figure 1) are made of the same material.
A
A nut needs to be tightened with a wrench.Which force shown in the figure will apply the greatest torque to the nut?
C
A machine part is made up of two pieces, with centers of gravity shown in the figure.
D
Use Newton's laws to find an expression for N, the normal force on each wheel.
N =mg/4
A baseball bat has a thick, heavy barrel and a thin, light handle.What should you do if you want to hold a baseball bat on your palm so that it balances vertically?
Put the end of the handle in your palm, with the barrel up
The figure below shows two blocks suspended by a single cord over a pulley. (Figure 1) The mass of block B is twice the mass of block A, while the mass of the pulley is equal to the mass of block A. The blocks are let free to move and the cord moves on the pulley without slipping or stretching. There is no friction in the pulley axle, and the cord's weight can be ignored.Which of the following statements correctly describes the system shown in the figure?
The angular acceleration of the pulley is nonzero.
What happens when block B moves downward?
The cord's tension on the right side of the pulley is higher than on the left side.
Choose a correct graph of the ball's angular velocity as a function of time for the first 3s of the ball's motion. By convention, clockwise rotations are negative and counterclockwise rotations are positive.
\____
Now assume that the frictional force fff is not at its maximum value. What is the relation between the torque ττtau applied to each wheel by the axles and the acceleration aaa of the car? Once you have the exact expression for the acceleration, make the approximation that the wheels are much lighter than the car as a whole.
a = 4τ/mr
If there is no slipping, a frictional force must exist between the wheels and the ground. In what direction does the frictional force from the ground on the wheels act? Take the positive x direction to be to the right.
positive x direction
Two horizontal rods are each held up by vertical strings tied to their ends. Rod 1 has length LL and mass MM; rod 2 has length 2LL and mass 2MM. Each rod then has one of its supporting strings cut, causing the rod to begin pivoting about the end that is still tied up.Which rod has a larger initial angular acceleration?
rod 1
A net torque applied to an object causes
the angular velocity of the object to change
If the sphere on the left is moved closer to the central cylinder and placed at a distance R/2 from the axis of rotation, what is the magnitude of the angular acceleration αalpha of the modified system? Assume that the rest of the system doesn't change.
α=2rF/3mR^2 b.) α=F/6mR
A small grinding wheel has a moment of inertia of 4.0×10−5 kg⋅m2kg⋅m2 . What net torque must be applied to the wheel for its angular acceleration to be 150 rad/s2
ττ = 6.0×10^−3 N⋅m
What is the net torque about the axle on the pulley in (Figure 1)? Express your answer in newton-meters.
-.20 n*m
The 3.2 kg, uniform, horizontal rod in (Figure 1) is seen from the side. What is the gravitational torque about the point shown?
-7.8 N⋅m
A typical compact disk has a mass of 15 gg and a diameter of 120 m.What is its moment of inertia about an axis through its center, perpendicular to the disk?
2.7×10−5kg⋅m2
Specifications require the oil filter for your car to be tightened with a torque of 30N⋅m. You are using a 15cm-long oil filter wrench, and you apply a force at the very end of the wrench in the direction that produces maximum torque.
200N
An object's moment of inertia is 1.7 kg⋅m2kg⋅m2 . Its angular velocity is increasing at the rate of 3.7 rad/sr per second.
6.3 N*m
Use Newton's laws to find an expression for the net external force acting on the car. Ignore air resistance.
Fnet =4f
