Answer:
Option D, they always point away from a north pole
Explanation:
Magnetic fields and electric fields are similar in following ways –
a) Electric field is produced by two opposite charges while magnetic field is produced by two opposite poles i.e north and South Pole. However, they are also produced by charges that are moving.
b) Like charges repel and unlike charges attract each other. Similarly, like poles repel and unlike poles attract each other
c) Electric field is pointed towards the positive charge while magnetic field is away from the north pole and move toward the south pole.
Hence, option D is correct
Answer:
No. Twice as much work will give the ball twice as much kinetic energy. But since KE is proportional to the speed squared, the speed will be 
times larger.
Explanation:
The work done on the ball is equal to the kinetic energy gained by the ball:
So when the work done doubles, the kinetic energy doubles as well:
However, the kinetic energy is given by
where
m is the mass of the ball
v is its speed
We see that the kinetic energy is proportional to the square of the speed, 
. We can rewrite the last equation as
which also means
If the work is doubled,
So the new speed is
So, the speed is 
times larger.
The stretch of the spring is
The constant of the spring is k=15 N/m, so we can find the force produced by the weight by using Hook's law:
The speed of sound is greater in ice (4000 m/s), then in water (1500 m/s), then in air (340 m/s). The explanation for this is the differente state of the matter in the three cases.
In fact, sound waves travel faster in solids (like ice), then in liquids (like water), then in gases (like air). This is because the speed of the sound wave depends on the density of the medium: the greater the density, the faster the sound wave. This can be easily understood by thinking at how a sound wave propagates: a sound wave is a vibration of molecules, which is transmitted throughout the medium by collision of the molecules. Therefore, the smaller the spacing between the molecules (such as in solids), the more efficient is the propagation, and so the sound wave is faster. On the contrary, there is a large spacing between molecules in gases (such as in the air), so there are less collisions between the molecules and so the wave is not transmitted efficiently, and so it has less velocity.
Answer:
B. Direction
Explanation:
Speed is a scalar quantity and doesn't keep track of direction : Velocity is a vector quantity and is direction aware.
