Answer:
a) The potential energy in the system is greatest at X.
Explanation:
Let be X the point where a ball rests at the top of a hill. By applying the Principle of Energy Conservation, the total energy in the physical system remains constant and gravitational potential energy at the top of the hill is equal to the sum of kinetic energy, a lower gravitational energy and dissipated work due to nonconservative forces (friction, dragging).

Conclusions are showed as follows:
a) The potential energy in the system is greatest at X.
b) The kinetic energy is the lowest at X and Z.
c) Total energy remains constant as the ball moves from X to Y.
Hence, the correct answer is A.
Answer:

Explanation:
We were told to calculate the speed of the ball,
Given speed of sound as 340 m
And we know that the sound of the ball hitting the pins is at 2.80 s after the ball is released from his hands.
Speed of ball = distance traveled/(time of hearing - time the sound travels).
Speed= S/t
Where S= distance traveled
t= time of hearing - time the sound travels
time=time for ball to roll+timefor sound to come back.
time of sound=16.5/340
=0.048529secs
solving for speedof ball
Then,Speed of ball = distance traveled/(time of hearing - time the sound travels).
=16.5/(2.80-0.048529) m/s = 5.997m/s
Therefore, the speed of the ball is
5.997m/s
It would be a cold wave.
Ice ages occur when the temperatures are extremely cold.(long-term)
Here when an object is placed on the level floor then in that case there are two forces on the object
1). Weight of object downwards (mg)
2). Normal force due to floor which will counterbalance the weight (N)
so when no force is applied on the box at that time normal force is counter balanced by weight.
Now here it is given that A person tried to lift the box upwards
So now there are two forces on the box
1). Applied force of person
2). Normal force due to ground
So now these two forces will counter balance the weight of the crate
So we can write an equation for force balance like

given that

here
m = 30 kg and
g = acceleration due to gravity = 10 m/s^2

now from above equation


So force applied by the person must be 150 N