Answer:
a = - 1.47 [m/s²], descending or going down
Explanation:
To solve this problem we must use Newton's second law which tells us that the sum of forces on a body is equal to the product of mass by acceleration.
∑F = m*a
where:
∑F = Forces applied [N]
m = mass = 10 [kg]
a = acceleration [m/s²]
Let's assume the direction of the upward forces as positive, just as if the movement of the box is upward the acceleration will be positive.
By performing a summation of forces on the vertical axis we obtain all the required forces and other magnitudes to be determined.
where:
g = gravity acceleration = 9.81 [m/s²]
N = normal force measured by the scale = 83.4 [N]
Now replacing:
![-(10*9.81)+83.4=10*a\\-14.7=10*a\\a=-1.47[m/s^{2} ]](https://tex.z-dn.net/?f=-%2810%2A9.81%29%2B83.4%3D10%2Aa%5C%5C-14.7%3D10%2Aa%5C%5Ca%3D-1.47%5Bm%2Fs%5E%7B2%7D%20%5D)
The acceleration has a negative sign, this means that the elevator is descending at that very moment.
The third one! :) Hope you live up to what ya promised man lol.
The original frequency of horn of Car A is 1071 Hz.
Explanation:
Doppler effect describes the change in the frequency of sound waves with respect to the observer. As the sound waves emitted from a source need to travel the air medium to reach observer, it will undergo loss in energy. So there will be change in its frequency compared to original frequency. Depending upon the direction of travel of source and observer the shifting of frequency will vary.
Here vo is the observer velocity and vs is the velocity of the source. So Vo = 15 m/s as car B is the observer and Vs = 35 m/s as car A is the source. And f is the frequency of sound wave at source that is car A.
Similarly, the doppler shift in frequency is the frequency of sound heard by car B which is f' = 1140 Hz. And v is the speed of sound that is v = 343 m/s
1140 = 
f = 1140/1.0649= 1071 Hz.
Thus, the original frequency of horn of Car A is 1071 Hz.
Get someone else to drive me
Answer:
Final speed of the box after it has moved to x = 10 is given as
v = 3.35 m/s
Explanation:
As we know by work energy theorem that work done by all the forces is equal to the change in its kinetic energy
Here work done by external force + work done by friction = change in kinetic energy of the box
so we have
![F x - \mu mg x = \frac{1]{2}mv^2](https://tex.z-dn.net/?f=F%20x%20-%20%5Cmu%20mg%20x%20%3D%20%5Cfrac%7B1%5D%7B2%7Dmv%5E2)
