#18). (I think. It's the one that starts with "Compare..." Gravity ALWAYS attracts. The force between electric charges can attract or repel ... it depends whether the charges are the same kind or opposite kinds.
#19). With both gravity and electric charges, the force between them quickly becomes weaker when the distance between them increases.
#20). I don't think it changes. If the doorknob gets charged by something that TOUCHES it, so that charges can flow into it from the other object or out of it, then the total amount of electric charge on it might change. But the question says that the doorknob is charged by an "electric field", so nothing touched it, and charges couldn't flow into it or out of it. The only way it got charged was by the charges it already had in it getting moved around ... electrons in one part of the knob moving over to the other side. Then it would act as if it was charged ... if you touched it, you might get zapped.
#21)., #22)., #23). You're supposed to draw a graph to answer these. It's a very easy graph to draw, and you should do it. Label the x-axis 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. Label the y-axis 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2 . Put the four points on the graph ... A, B, C, and D. For each point, the 'battery voltage' is the number on the x-axis and the 'Current' is the number on the y-axis. Then draw a line through the points. When you have the graph to look at, you can easily answer 21, 22, and 23.
24). I'm not sure, and I don't want to guess.
25). Did you ever move a coil of wire near a magnet in class ? This is the same situation, only the magnet is moving and the wire is still. The result will be the same.
26). Magnets have two poles that attract the opposite kind and repel. Now you copy the map and fill in the other side.
This is a lot of work for 5 points, so I left some parts for you to do. Another reason I did that is: You'll learn a lot more that way.
angle of projection of the book from the horizontal,
a)
velocity of the student before throwing the book:
Since the student is initially at rest and no net force acts on the student so it remains in rest according to the Newton's first law of motion.
where:
initial velocity of the student
velocity of the student after throwing the book:
Since the student applies a force on the book while throwing it and the student standing on the skate will an elastic collision like situation on throwing the book.
where:
final velcotiy of the student after throwing the book
b)
c)
Since there is no movement of the student in the vertical direction, so the total momentum transfer to the earth will be equal to the momentum of the book in vertical direction.
Magnetism is <span>a physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces between objects.</span>
The evidence that supports continental drift and plate tectonics includes different fossils, the same rocks and the shapes of continents that fit together.
<h3>What is continental drift?</h3>
Continental drift is a theory that states continents once were part of one big landmass known as Pangea.
Nowadays, the theory of continental drift proposed by Alfred Wegener has been replaced by plate tectonics.
In conclusion, the evidence that supports continental drift and plate tectonics includes fossils, the same rocks and the shapes of continents that fit together.
