19. Two waves traveling in opposite directions on a rope meet and undergo complete destructive interference.

If you dribble a basketball with a frequency of 1.77 Hz, how long does it take for you to complete 12 dribbles?

Licemer1 [7]

<h2>It takes 6.78 seconds to complete 12 dribbles.</h2>

Explanation:

Frequency of dribble = 1.77 Hz

That is

Number of dribbles in 1 second = 1.77

$\texttt{Time taken for 1 dribble = }\frac{1}{1.77}=0.565s$

Now we need to find how long does it take for you to complete 12 dribbles.

Time taken for 12 dribbles = 12 x Time taken for 1 dribble

Time taken for 12 dribbles = 12 x 0.565

Time taken for 12 dribbles = 6.78 seconds

It takes 6.78 seconds to complete 12 dribbles.

8 0

2 years ago

A box is placed on a conveyor belt that moves with a constant speed of 1.05 m/s. The coefficient of kinetic friction between the

sveticcg [70]

Answer:

The box stops in 0.139 seconds, after moving 7.29cm (0.0729m) backwards relative to the belt.

Explanation:

As the box is initially at rest relative to the earth, it is moving backwards with a speed of 1.05m/s relative to the belt. Then, the frictional force acts on the box to make it stop relative to the belt. So, we first have to write the equations of motion of the box in each axis:

$x: f_k=ma\implies a=\frac{f_k}{m} \\\\y: N-mg=0\implies N=mg$

Since the frictional force $f_k$ is equal to $f_k=\mu_k N=\mu_k mg$ , then we have that the acceleration is:

$a=\frac{\mu_k mg}{m}=\mu_k g$

Now, from the definition of acceleration we get:

$a=\frac{v-v_0}{t}\implies t=\frac{v-v_0}{a}$

And, as the final velocity is zero because the box gets to a stop, we have:

$t=-\frac{v_0}{a}=-\frac{v_0}{\mu_k g}$

(Don't worry about the negative sign. It will disappear because the initial velocity is also negative, since we take the box initially moving backwards)

Then, plugging in the given values, we calculate the time:

$t=-\frac{(-1.05m/s)}{0.770(9.81m/s^{2})}=0.139s$