Answer: A
si, di, are expressed as negative and f is expressed as positive values.
Explanation:
When the object is located at a location in front of the focal point of a convex len, the image will always be located somewhere on the same side of the lens as the object. The image is located behind the object. In this case, the image will be an upright image and the image is enlarged
In this question, the relationship between the focal length, image distance di and object distance is
I/f = 1/di + 1/do that is
I/f - 1/di - 1/do = 0
The image size si is also negative since the image is a virtual image.
Therefore, si, di, are expressed as negative, f is expressed as positive values.
Answer:

Explanation:
We'll use the momentum equation:

where:
p = momentum
m = mass
v = velocity
Since we're doing the magnitude of momentum of the system, we'll add the mass of the cyclist and the mountain bike together:

Given that, we can now substitute our given values into the momentum equation:

Our final answer is:

Frictional force offers the resistance to the applied force opposing its motion. Thus, it always acts in the direction opposite to that of the object in motion. If force is applied to the left, then friction acts in the right.
Answer:
Getting rid of outdated information from the brain.
Explanation:
In the brain, storing and losing memory are two important things in selecting and holding relevant information. Forgetting is a way of dealing with unneeded information in the brain thus absent minded individuals have an improved brain flexibility because their brain removes unwanted and unnecessary information regularly.