The correct answer is A. B. C. Hope this helps!!
Answer: b) they are the areas where Earth's magnetic field is weakest
Explanation:
According to classical physics, a magnetic field always has two associated magnetic poles (north and south), the same happens with magnets. This is because for <em>classical physics</em>, naturally, magnetic monopoles can not exist.
In this context, Earth is similar to a magnetic bar with a north pole and a south pole. This means, the axis that crosses the Earth from pole to pole is like a big magnet.
Now, by convention, on all magnets the north pole is where the magnetic lines of force leave the magnet and the south pole is where the magnetic lines of force enter the magnet. Then, for the case of the Earth, the north pole of the magnet is located towards the geographic south pole and the south pole of the magnet is near the geographic north pole.
Being the magnetic poles the places where the Earth's magnetic field is weakest. And it is for this reason, moreover, that the magnetic field lines enter the Earth through its magnetic south pole (which is the geographic north pole).
Answer:
The minimum speed of the box bottom of the incline so that it will reach the skier is 8.19 m/s.
Explanation:
It is given that,
Mass of the box, m = 2.2 kg
The box is inclined at an angle of 30 degrees
Vertical distance, d = 3.1 m
The coefficient of friction, 
Using the work energy theorem, the loss of kinetic energy is equal to the sum of gain in potential energy and the work done against friction.
W is the work done by the friction.
v = 8.19 m/s
So, the speed of the box is 8.19 m/s. Hence, this is the required solution.
Answer:
C. 39 m/s
Explanation:
First we need to calculate the total force required to move the train along the inclined plane. So, it is clear that the work done will be equal to the component of the weight that is parallel to the inclined plane, because there is no frictional force present:
Force = F = mg Sin θ
where,
m = mass of train = 3.3 x 10⁶ kg
g = 9.8 m/s²
θ = Angle of Inclination = 0.64°
Therefore,
F = (3.3 x 10⁶ kg)(9.8 m/s²)Sin 0.64°
F = 3.612 x 10⁵ N
Now, the formula for power is:
P = FV
V = P/F
where,
V = Velocity of Train = ?
P = Power of Engine = 14 MW = 1.4 x 10⁷ W
Therefore,
V = 1.4 x 10⁷ W/3.612 x 10⁵ N
V = 38.75 m/s
which is approximately equal to:
<u>C. 39 m/s</u>
