You are pushing an 80.0 N wheelbarrow as shown in (Figure 1). You lift upward on the handle of the wheelbarrow so that the only
point of contact between the wheelbarrow and the ground is at the front wheel. Assume the distances are as shown in the figure, where 0.50 m is the horizontal distance from the center of the wheel to the center of gravity of the wheelbarrow. The center of gravity of the dirt in the wheelbarrow is assumed to also be a horizontal distance of 0.50 m from the center of the wheel. Suppose that the maximum total upward force that you can apply to the wheelbarrow handles is 75 lb.
1 answer:
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If we neglect frictional force, the total mechanical energy of the ball is conserved.
The total mechanical energy of the ball is the sum of its kinetic energy K and its potential energy U:
where the kinetic energy depends on the speed v of the ball:
while the potential energy depends on the height h at which the ball is:
As the ball travels along the roller coaster, there is a continuous conversion between kinetic and potential energy, because the total mechanical energy E has always the same value. Therefore, when the ball goes on top of a hill, its height h increases and its potential energy U increases as well, while the speed v decreases and K decreases. Vice-versa, when the ball reaches the bottom of a hill, its height h decreases and therefore the potential energy U decreases, while the speed v increases and therefore the kinetic energy K of the ball increases as well.
The total mechanical energy of the ball is the sum of its kinetic energy K and its potential energy U:
where the kinetic energy depends on the speed v of the ball:
while the potential energy depends on the height h at which the ball is:
As the ball travels along the roller coaster, there is a continuous conversion between kinetic and potential energy, because the total mechanical energy E has always the same value. Therefore, when the ball goes on top of a hill, its height h increases and its potential energy U increases as well, while the speed v decreases and K decreases. Vice-versa, when the ball reaches the bottom of a hill, its height h decreases and therefore the potential energy U decreases, while the speed v increases and therefore the kinetic energy K of the ball increases as well.
A uniform disk is constrained to rotate about an axis passing through its center and perpendicular to the plane of the disk. If the disk starts from rest and is then brought in contact with a spinning rubber wheel, we observe that the disk gradually begins to rotate too. If after 35 s of contact with this spinning rubber wheel, the disk has an angular velocity of 4.0 rad/s, find the average angular acceleration that the disk experiences. (Assume the positive direction is in the initial direction of rotation of the disk. Indicate the direction with the sign of your answer.)
Assume after 35 s of contact with this spinning rubber wheel, the disk has an angular velocity of 11.0 rad/s.
Answer:
385 rad
Explanation:
The expression for the angular acceleration of a disk that is in contact with a spinning wheel can be given as:
where =
Angular displacement of a disk can be calculated by using the formula:
substituting 11.0 rad/s for and t = 35 s ; we have: