Answer:
Explanation:
Provided:
The trolley, with mass M, is allowed to roll freely without friction.
The coefficient of friction between the trolley and mass m is
.
A force F is applied to mass m.
The acceleration of the system is

The frictional force will counterbalance the weight of the block.
The frictional force is 





Answer:
31.4 mm²
Explanation:
The ability of a telescope or eye to gather light can be expressed by the formula,

where d signifies the diameter of the pupil.
In bright daylight, the usual size of the pupil is 3 mm.

Conversely, in darkness, the diameter typically enlarges to 7 mm.

This indicates an increase in light-gathering capacity.

Thus, the amount of light the eye can capture is 31.4 mm².
The astronaut's speed is described in the sentence. The astronaut moves at a rate of 10 meters each minute. To clarify: speed is defined as distance divided by time and is characterized solely by its magnitude, not its direction. Hence, the 10 meters per minute reflects this. We lack information about the astronaut's directional movement. In contrast to speed, velocity incorporates direction as well; for instance, a velocity of 10m/s due west provides a directional context. Consequently, without specified direction, the value indicated is merely speed.