Answer:
distance between the dime and the mirror, u = 0.30 m
Given:
Radius of curvature, r = 0.40 m
magnification, m = - 2 (since,inverted image)
Solution:
Focal length is half the radius of curvature, f =
f =
Now,
m = -
- 2 = -
= 2 (2)
Now, by lens maker formula:
v = (3)
From eqn (2):
v = 2u
put v = 2u in eqn (3):
2u =
2 =
2(u - 0.20) = 0.20
u = 0.30 m
Answer:
Explanation:
The angular momentum of an object in rotation is given by
where
I is the moment of inertia
is the angular speed
In this problem, initially we have
is the moment of inertia of the wheel
is the initial angular speed
So the initial angular momentum is
Later, a counterclockwise torque of
is applied
So the angular acceleration of the wheel is:
in the direction opposite to the initial rotation.
As a result, the final angular velocity of the wheel will be:
where
t = 4.0 is the time interval
Solving,
which means that now the wheel is rotating in the counterclockwise direction.
Therefore, the new angular momentum of the wheel is:
So, the change in angular momentum is: