To solve this problem we must apply the concepts related to Tangential Acceleration based on angular velocity and acceleration, and therefore, we must also calculate angular velocity based on the given frequency. For all these problems we will take the Units to the International System. The maximum acceleration would then be defined as,

Here,
= Angular velocity
A = Amplitude
At the same time the angular velocity is described as,

Here f means the frequency of the wave. Substituting,




Replacing at the first equation,


Therefore the maximum particle acceleration for a point on the string is 
Answer:
Plane mirror is similar to a concave mirror
The impulse is given by the magnitude of the force times the time interval:

We can see that the force F of the 4 skateboard is always the same (33 N), this means that the skateboard with greatest impulse is the one with the largest time interval, so skateboard C).
Answer:
The force due to friction is generally independent of the contact area between the two surfaces. This means that even if you have two heavy objects of the same mass, where one is half as long and twice as high as the other one, they still experience the same frictional force when you drag them over the ground.
Explanation:
Independent