A 0.26-kg rock is thrown vertically upward from the top of a cliff that is 32 m high. when it hits the ground at the base of the
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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:
Answer:
acceleration 8 km/h/s south
Explanation:
First of all, let's remind that a vector quantity is a quantity which has both a magnitude and a direction.
Based on this definition, we can already rule out the following two choices:
distance: 40 km
speed: 40 km/h
Since they only have magnitude, they are not vectors.
Then, the following option:
velocity: 5 km/h north
is wrong, because the car is moving south, not north.
So, the correct choice is
acceleration 8 km/h/s south
In fact, the acceleration can be calculated as
where
v = 40 km/h is the final velocity
u = 0 is the initial velocity
t = 5 s is the time
Substituting,
And since the sign is positive, the direction is the same as the velocity (south).