Answer:
3.5 hours
Explanation:
Speed = distance/time
Let the distance that Fiora biked at 20 mi/h through be x miles and the time it took her to bike through that distance be t hours at 20 mi/h
Then, the rest of the distance that she biked at 14 mi/h is (112 - x) miles
And the time she spent biking at 14 mi/h the rest of the distance = (6.5 - t) hours
Her first biking speed = 20 mph = 20 miles/hour
Speed = distance/time
20 = x/t
x = 20 t (eqn 1)
Her second biking speed = 14 mph = 14 miles/hour
14 = (112 - x)/(6.5 - t)
112 - x = 14 (6.5 - t)
112 - x = 91 - 14t (eqn 2)
Substitute for x in (eqn 2)
112 - 20t = 91 - 14t
20t - 14t = 112 - 91
6t = 21
t = 3.5 hours
x = 20t = 20 × 3.5 = 70 miles.
(112 - x) = 112 - 70 = 42 miles
(6.5 - t) = 6.5 - 3.5 = 3 hours
Meaning that she travelled at 20 mi/h for 3.5 hours.
Explanation:
d) Magnetic force is the power that pulls materials together (magnet e. g iron)
an example :how magnet can pick up a coin.
e) frictional force produces when two surfaces are in contact with each other.
effects of friction : I) it produces heat
II) it causes loss in power.
Answer:
allow the downward movement of the concentration gradient by passive transport
Explanation:
Passive transport is a process of substance transport, which is carried out spontaneously, without energy expenditure and in favor of the concentration gradient, that is, from a medium where the molecules are more concentrated towards a medium where their concentration is lower.
Three types of passive transport are distinguished: osmosis, simple diffusion and facilitated diffusion
<u>Simple diffusion</u>
It is the passage, through the plasma membrane, of small molecules without charge soluble in the lipid bilayer, such as some gases (oxygen and carbon dioxide). For a molecule to diffuse through the membrane it is necessary that there is a difference in concentration between the external and the internal environment.
<u>Diffusion facilitated
</u>
There are molecules such as amino acids, glucose and small ions that, due to their chemical and size characteristics, cannot diffuse through the lipid bilayer and require transport proteins for diffusion.
The transport proteins are immersed in the plasma membrane and can be of two types: protein channels, formed by proteins that generate a channel in the membrane, and permeases, which are proteins that, when joined to the molecule to be transported, change their shape by carrying them into the cell.
Answer:
d = 120 [m]
Explanation:
In order to solve this problem, we must use the theorem of work and energy conservation. Where the energy in the final state (when the skater stops) is equal to the sum of the mechanical energy in the initial state plus the work done on the skater in the initial state.
The mechanical energy is equal to the sum of the potential energy plus the kinetic energy. As the track is horizontal there is no unevenness, in this way, there is no potential energy.
E₁ + W₁₋₂ = E₂
where:
E₁ = mechanical energy in the initial state [J] (units of Joules)
W₁₋₂ = work done between the states 1 and 2 [J]
E₂ = mechanical energy in the final state = 0
E₁ = Ek = kinetic energy [J]
E₁ = 0.5*m*v²
where:
m = mass = 60 [kg]
v = initial velocity = 12 [m/s]
Now, the work done is given by the product of the friction force by the distance. In this case, the work is negative because the friction force is acting in opposite direction to the movement of the skater.
W₁₋₂ = -f*d
where:
f = friction force = 36 [N]
d = distance [m]
Now we have:
0.5*m*v² - (f*d) = 0
0.5*60*(12)² - (36*d) = 0
4320 = 36*d
d = 120 [m]
The resultant force on the system is equivalent to the difference in the weights of the chandelier and Robin Hood.
F(net) = 240g - 85g
F(net) = 155g
Robin Hood's Acceleration:
F = ma
155g = 85a
a = 17.89 m/s²
Tension = mg + ma
Tension = 85(g + a)
Tension = 2400 N
