Answer: More friction
Explanation: The wood would probably splinter, causing even more friction, while the metal would probably smooth the wood out.
Answer:
Driving force increases, friction forces increase, the driving force is bigger than friction 12.
Explanation:
Double
Explanation:
Since the period T of a pendulum is given by

By increasing the length of the pendulum by 4, the period becomes

You can see that the period doubles when we increase the length by a factor of 4.