The formula for a kinetic energy KE of a falling body is
KE = mgh
where m = mass, g = acceleration due to gravity (9.8 m/s^2, constant), h = height.
The total mass of a skateboader and a skateboard is 64 + 2.0 = 66 kg.
Finally,
KE = 66*9.8*5.0 = 32340 J
Answer:
Even though CFL are more expensive, they tend to last longer. Research proves that CFL uses 1/4 to 1/3 the same amount of energy to produce the same lighting as an incandescent light bulb (source: enhso.com)
Answer:
B negatively charged. C negatively charged. D positively charged.
Explanation:
If A Is negative and B is repelled by it this means that B has to have the same charge as A therefore B is negatively charged.
B is repelled By C therefore meaning they both have the same charge so C has to be negatively charged.
B is attracted to D. attraction occurs between oppositely charged objects. Therefore D has to have the opposite charge of B. Since B is negative D has to be positive in order for that attraction to occur.
Answer:
The center of mass is at + 37.11 cm
Solution:
As per the question:
Length of the rod, l = 1 m = 100 cm
Density of Brass, ![\rho_{B} = 8.44\ g/cm^{3}](https://tex.z-dn.net/?f=%5Crho_%7BB%7D%20%3D%208.44%5C%20g%2Fcm%5E%7B3%7D)
Density of Aluminium, ![\rho_{Al} = 2.7\ g/cm^{3}](https://tex.z-dn.net/?f=%5Crho_%7BAl%7D%20%3D%202.7%5C%20g%2Fcm%5E%7B3%7D)
Distance from the mid point to each, r = 50 cm
Now,
The center of mass with the origin at mid point is given by the expression:
![X_{CoM} = \frac{\int_{0}^{50} \rho_{B} rdr + \int_{100}^{50} \rho_{Al} rdr}{M_{B}r + M_{Al}r}](https://tex.z-dn.net/?f=X_%7BCoM%7D%20%3D%20%5Cfrac%7B%5Cint_%7B0%7D%5E%7B50%7D%20%5Crho_%7BB%7D%20rdr%20%2B%20%5Cint_%7B100%7D%5E%7B50%7D%20%5Crho_%7BAl%7D%20rdr%7D%7BM_%7BB%7Dr%20%2B%20M_%7BAl%7Dr%7D)
![X_{CoM} = \frac{\rho_{B}\frac{r^{2}}{2}]_{0}^{50} + \rho_{Al}\frac{r^{2}}{2}]_{100}^{50}}{M_{B}r + M_{Al}r}](https://tex.z-dn.net/?f=X_%7BCoM%7D%20%3D%20%5Cfrac%7B%5Crho_%7BB%7D%5Cfrac%7Br%5E%7B2%7D%7D%7B2%7D%5D_%7B0%7D%5E%7B50%7D%20%2B%20%5Crho_%7BAl%7D%5Cfrac%7Br%5E%7B2%7D%7D%7B2%7D%5D_%7B100%7D%5E%7B50%7D%7D%7BM_%7BB%7Dr%20%2B%20M_%7BAl%7Dr%7D)
![X_{CoM} = \frac{8.44\frac{2500}{2}] + 2.7\frac{7500}{2}]{8.44\times 50 + 2.7\times 50}](https://tex.z-dn.net/?f=X_%7BCoM%7D%20%3D%20%5Cfrac%7B8.44%5Cfrac%7B2500%7D%7B2%7D%5D%20%2B%202.7%5Cfrac%7B7500%7D%7B2%7D%5D%7B8.44%5Ctimes%2050%20%2B%202.7%5Ctimes%2050%7D)
![X_{CoM} = + 37.11\ cm](https://tex.z-dn.net/?f=X_%7BCoM%7D%20%3D%20%2B%2037.11%5C%20cm)