Answer:
33 seconds.
Explanation:
The equation for speed with constant acceleration at time t its:

where
is the initial speed, and a its the acceleration.
<h3>First half of the problem</h3>
Starting at rest, the initial speed will be zero, so

the final speed is

and the acceleration is
.
Taking all this together, we got




So, for the first half of the problem we got a time of 10 seconds.
<h3>Second half of the problem</h3>
Now, the initial speed will be
,
the acceleration
,
with a minus sign cause its slowing down, the final speed will be

Taking all together:




So, for the first half of the problem we got a time of 23 seconds.
<h3>Total time</h3>

Answer: No
Explanation:
The number of neutrons is equal to the difference between the mass number of the atom (M) and the atomic number (Z).
Answer:
r = 22.3 cm
Explanation:
given,
angular speed = 45 rev/s
tangential speed = 63 m/s
length of the rotating string
angular velocity =
ω = 2 π N
ω = 2 π x 45
ω = 282.74 rad/s
we know,
v = r ω



r = 22.3 cm
Answer:
F = 9.81 [N]
Explanation:
To solve this problem we must use Newton's third le which tells us that the sum of forces on a body that remains static must be equal to one resulting from these forces in the opposite direction.
Let's perform a summation of forces on the vertical axis-y to determine the normal force N.
∑F = 0 (axis-y)

where:
m = mass = 4 [kg]
g = gravity acceleration = 9.81 [m/s²]
![N - (4*9.81)=0\\N = 39.24 [N]](https://tex.z-dn.net/?f=N%20-%20%284%2A9.81%29%3D0%5C%5CN%20%3D%2039.24%20%5BN%5D)
Now we know that the frictional force can be calculated using the following equation.
f = μ*N
where:
f = friction force [N]
μ = friction coefficient = 0.25
N = normal force = 39.24 [N]
Now replacing:
![f = 0.25*39.24\\f = 9.81[N]](https://tex.z-dn.net/?f=f%20%3D%200.25%2A39.24%5C%5Cf%20%3D%209.81%5BN%5D)
Then we perform a sum of forces on the X-axis equal to zero. This sum of forces allows us to determine the minimum force to be able to move the object in a horizontal direction.
∑F = 0 (axis-x)
![F-f=0\\F-9.81=0\\F= 9.81[N]](https://tex.z-dn.net/?f=F-f%3D0%5C%5CF-9.81%3D0%5C%5CF%3D%209.81%5BN%5D)
If the coefficient was smaller, a smaller force (F) would be needed to start the movement, this can be easily seen by replacing the value of 0.25, by smaller values, such as 0.1 or 0.05.
If the coefficient were larger, a larger force would be needed.
The north arrow of the compasses will all point to the south since opposite poles attract. I have put an example picture below.
For the horse shoe magnet the magnetic field line will also go from north to south. I have put a picture of this below