no, it not useless. we still learn Bohr's model in HS n dats almost 200 yr old! while there may be new models, previous one is good for explaining the basics. it is also useful to learn previous model n see how our understanding improves over time.
Gravity is a force because it pulls down on objects.
Answer:
B. Attract each other with a force of 10 newtons.
Explanation:
Statement is incorrectly written. <em>The correct form is: A </em>
<em> charge and a </em>
<em> at a distance of 0.3 meters. </em>
The two particles have charges opposite to each other, so they attract each other due to electrostatic force, described by Coulomb's Law, whose formula is described below:
(1)
Where:
- Electrostatic force, in newtons.
- Electrostatic constant, in newton-square meters per square coulomb.
- Magnitudes of electric charges, in coulombs.
- Distance between charges, in meters.
If we know that
,
and
, then the magnitude of the electrostatic force is:


In consequence, correct answer is B.
Answer:
0.0021576N
Explanation:
F=(k)(q1q2/r^2)
F=(8.99×10^9)(3×10^-6)(2×10^-6)/(5^2)
F=0.0021576N
Answer:
w = 5832.372 Joules
Explanation:
Mass of water, m = 20 kg
The water was pulled up to a height of 35 meters, i.e. h = 35 m
It takes 14 minutes to pull up the water through the height, 35 m
speed = distance/ time = 35/14 = 2.5 m/min
The bucket's height, y = speed * time = 2.5t meters
6 kg of water drips out of the bucket throughout the 14 minutes
The rate at which the water drips drips out = (6/14) = 0.4286 kg/min
Mass of water that drips out in time, t = 0.4286t kg
The mass of water remaining = (20 - 0.4286t) kg
Change in Workdone, Δw = mgΔy
Δy = 2.5 Δt
Δw = mg * 2.5 Δt
dw = (20 - 0.4286t)g2.5 dt
integrating both sides
dw = (50g - 1.07gt)dt
where b = 0, a = 14
w = 50gt - 1.07g(t²)/2 g = 9.8 m/s²
w = 490t - 5.243t²
w = (490*14 - 5.243*14²) - (490*0 - 5.243*0²)
w = 6860 - 1027.628
w = 5832.372 Joules