Answer:
Part a)

Part b)
t = 12 s
Explanation:
Part a)
Tension in the rope at a distance x from the lower end is given as

so the speed of the wave at that position is given as

here we know that

now we have


Part b)
time taken by the wave to reach the top is given as




The car's speed is 240km/4hr= 60km/hr.
There's not enough information given in the question to determine its velocity.
The correct answer is A. Solid Rock
Answer: B
Explanation:
An unbalanced force (net force) acting on an object changes its speed and/or direction of motion. An unbalanced force is an unopposed force that causes a change in motion.