Science 8B - Sample Work
Unit 5 - Non-Contact Forces
Question 1: Define non-contact forces and give three examples.
Answer: Non-contact forces are forces that act on objects from a distance without any physical contact between them. Three examples of non-contact forces are gravitational force, electrostatic force, and magnetic force.
Question 2: Describe the difference between electric charges that are attracted to each other and electric charges that are repelled from each other.
Answer: Electric charges that are attracted to each other are of opposite polarities, i.e., one charge is positive and the other is negative. Electric charges that are repelled from each other are of the same polarity, i.e., both charges are either positive or negative.
Question 3: Explain how a Van de Graaff generator works.
Answer: A Van de Graaff generator works by using a moving belt to transfer charges from a grounded electrode to an insulated metal sphere. The sphere accumulates an electric charge due to the friction between the belt and the electrode, and the charge is transferred to the sphere via a metal comb. The charge on the sphere can be very high, and it can cause objects nearby to be attracted or repelled, depending on their electric charges.
Question 4: If two magnets are brought close to each other, what happens? Give an example.
Answer: If two magnets are brought close to each other, they can either attract or repel each other, depending on their orientations. For example, if a north pole of one magnet is brought close to the south pole of another magnet, they will attract each other. However, if the north pole of one magnet is brought close to the north pole of another magnet, they will repel each other.