Answer:
<em>Option b is correct: 4.1 s</em>
Explanation:
<u>Vertical Launch</u>
An object launched thrown vertically upward where air resistance is negligible, reaches its maximum height in a time t, given by the equation:
![\displaystyle t=\frac{v_o}{g}\qquad\qquad[1]](https://tex.z-dn.net/?f=%5Cdisplaystyle%20t%3D%5Cfrac%7Bv_o%7D%7Bg%7D%5Cqquad%5Cqquad%5B1%5D)
Where vo is the initial speed and g is the acceleration of gravity g=9.8 
.
Once the object reaches that point, it starts a free-fall motion, whose speed is (downward) given by:
![v_f=g.t\qquad\qquad[2]](https://tex.z-dn.net/?f=v_f%3Dg.t%5Cqquad%5Cqquad%5B2%5D)
The object considered in the question is thrown with vo=25 m/s. The time taken to reach the maximum height is given by [1]:
The object starts its falling motion and at some time, it has a speed of vf=15 m/s. Let's find the time by solving [2] for t:
The total time taken by the object to go up and down is
a. This option is incorrect because it's far away from the answer.
d. This option is incorrect because it's far away from the answer.
b. This option is correct because it's a good approximation to the calculated answer.
e. This option is incorrect because it's far away from the answer.
c. This option is incorrect because it's far away from the answer.
Complete question:
A fireman of mass 80 kg slides down a pole. When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s. By how much has thermal energy increased during his slide?
Answer:
The thermal energy increased by 3,099.2 J
Explanation:
Given;
mass of the fireman, m = 80 kg
initial position of the fireman, hi = 4.2 m
final speed, v = 2.2 m/s
The change in the thermal energy is calculated as;
ΔE + (K.Ef - K.Ei) + (Uf - Ui) = 0
where;
ΔE is the change in the thermal energy
K.Ef is the final kinetic energy
K.Ei is the initial kinetic energy
Uf is the final potential energy
Ui is the initial potential energy
Answer:
it most likly right I'm not 100% sure
Answer:
Primary waves (P-waves)
Explanation:
Due to excess of the energy inside the earth when the tectonic plates begin to slide or fracture then the energy is released in the form of seismic waves, this causes the earthquake.
<u>Two types of seismic waves are generally responsible for the earth quakes:</u>
- body waves
- surface waves
Body waves are of two types:
Primary waves (P-waves)
These are the fastest of all the waves involved in the earth-quake which travel at a speed of 1.6 km to 8 km per second.
They can pass trough solids, liquids and gases. They arrive at the surface as an instant thud.
Secondary waves (S-waves)
They can only pass through the solids and they move slower than the P-waves.
As S-waves move, they displace the rock particles, pushing them outwards perpendicular to the wave-path that leads to the earthquake-related first rolling period.
Surface waves (L-waves/ long waves)
- These waves move along the surface of the earth. They are responsible for the earthquake's carnage.
- They move up and down the Earth's surface, rocking the foundations of man-made structures.
- Surface waves are slowest of the three waves, which means that they are the last to arrive. So at the end of an earthquake usually comes the most powerful shaking.
