Answer : The restoring force is directly proportional to the displacement of the block.
Explanation :
Restoring force is defined as the force that is exerted by the spring due to its mass.
Mathematically, the restoring force can be written as :

F = - k x
where,
k is the spring constant.
x is the displacement caused due to the mass.
Negative sign shows that the force is acting in opposite direction.
So, it is clear that the restoring force is directly proportional to the displacement of the block.
Hence, the correct option is (b) " The restoring force is directly proportional to the displacement of the block ".
You will have to use this formula:

Final Velocity (V) = 4m/s
Initial Velocity (Vo) = 8m/s
Acceleration (a) = ? m/s^2
Time (t) = 2 secs
Then:
-> 4 = 8 + a x 2
-> 4 - 8 = 2a
-> -4 = 2a
-> a = -4/2
-> a = -2 m/s^2
Ps: It's value is negative because the she was in retrograde motion.
Answer: Her acceleration is -2 m/s^2.
We use the kinematic equations,
(A)
(B)
Here, u is initial velocity, v is final velocity, a is acceleration and t is time.
Given,
,
and
.
Substituting these values in equation (B), we get
.
Therefore from equation (A),

Thus, the magnitude of the boat's final velocity is 10.84 m/s and the time taken by boat to travel the distance 280 m is 51.63 s
<span>After entering the loop, it should use the correct list size and the loop will be affected if the remove call changes the size of the list.
If lst is an Arraylist the running time of removefirsthalf is O (n^2). So when the beginning is removed the next element will move forward.
If lst is a LinkedList which is a dynamic structure the running is O (n) for removefirsthalf</span>
Simply subtract the two velocities and divide by 8.1,

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I hope that helps you out!!
Any more questions, please feel free to ask me and I will gladly help you out!!
~Zoey