Answer: 
Explanation:
Given
Length of plank is 1.6 m
Force
is applied on the left side of plank
Force
is applied 43 cm from the left end O.
Mass of the plank is 
for equilibrium
Net torque must be zero. Taking torque about left side of the plank

Net vertical force must be zero on the plank

, density is how compact an object is. Put another way, density is the mass of an object divided by its volume.
Answer:
48.16 %
Explanation:
coefficient of restitution = 0.72
let the incoming speed be = u
let the outgoing speed be = v
kinetic energy = 0.5 x mass x 
- incoming kinetic energy = 0.5 x m x
- coefficient of restitution =

0.72 =
v = 0.72u
therefore the outgoing kinetic energy = 0.5 x m x 
outgoing kinetic energy = 0.5 x m x 
outgoing kinetic energy = 0.5184 (0.5 x m x
)
recall that 0.5 x m x
is our incoming kinetic energy, therefore
outgoing kinetic energy = 0.5184 x (incoming kinetic energy)
from the above we can see that the outgoing kinetic energy is 51.84 % of the incoming kinetic energy.
The energy lost would be 100 - 51.84 = 48.16 %
Answer:
4*10^-2
Explanation:
for the scientific notation the first number must be between 1 and 10, so in this case it is 4. 4/100 is also equal to 0.04, and if we could the number of places before 4, there are two, therefore 4 times 10 to the power of -2