Use the law of energy conservation. When the elevator hits the spring, it has a certain kinetic and a potential energy. When the elevator reaches the point of still stand the kinetic and potential energies have been transformed to work performed by the elevator in the form of friction (brake clamp) and loading the spring.

Let us define the vertical height axis as having two points: h=2m at the point of elevator hitting the spring, and h=0m at the point of stopping.

The total energy at the point h=2m is:

$E_{tot}=E_{kin}+E_{pot}\\E_{tot}= \frac{1}{2}mv^2+mg\Delta h = \frac{1}{2}2000 kg 4^2\frac{m^2}{s^2}+2000kg\, 9.8\frac{m}{s^2}2m=55200\,kg\frac{m^2}{s^2}$

The total energy at the point h=0m is:

$E_{tot}=E_{kin}+E_{pot}+Work=0+0+ Work\\E_{tot} =F_{friction}\Delta h+\frac{1}{2}k (\Delta h)^2=17000N\cdot 2m+\frac{1}{2}k\cdot 2^2 m^2$

The two Energy values are to be equal (by law of energy conservation), which allows us to determine the only unknown, namely the force constant k:

$17000N\cdot 2m+\frac{1}{2}k\cdot 2^2 m^2 = 55200 \,kg\frac{m^2}{s^2}\\k = \frac{55200-34000}{2}\,\frac{kg}{s^2}=10600\frac{kg}{s^2}$

5 0

3 years ago

An student in a swimming pool weighs 450 N and in a regular balance out of the swimming pool weighs 700 N. What is the value of

rewona [7]

The value of buoyant force is 700-450=300N

7 0

3 years ago

Help ASAP with equation and answer pls. Numbers 2 3 4

scoray [572]

Answer:

2. 200N

3.50kg

4.700N

Explanation:

Weight is another word for the force of gravity

Weight is a force that acts at all times on all objects near Earth.

F=m*g

where g=acceleration due to gravity

2. due to the gravitational fields of the earth , assume gravitational acceleration=10m/s2

F=20*10= 200N

3.same as above

mass=Force/gravitational acceleration

mass=500/10 = 50kg

4.force=mass*gravitational acceleration

force=70*10=700N

8 0

2 years ago

Which of the following is a technique for the effective communication? ​

Which of the following is a technique for the effective communication?