Answer : The total work done in raising the ball is, 0.98 J
Explanation : Given,
Mass of the ball = 0.075 kg
Height raised of the ball = 1.33 m
As we know that the object is moving with the constant velocity, that means the work done against the gravity will be the net-work done.
So, the work done will be:
where,
w = work done
m = mass of ball
h = height of ball
g = acceleration due of gravity = 
Now put all the given values in the above formula, we get:
Thus, the total work done in raising the ball is, 0.98 J
Copper conducts electricity
Answer:
Final Speed of Dwayne 'The Rock' Johnson = 15.812 m/s
Explanation:
Let's start out with finding the force acting downwards because of the mass of 'The Rock':
Dwayne 'The Rock' Johnson: 118kg x 9.81m/s = 1157.58 N
Now the problem also states that the kinetic friction of the desk in this problem is 370 N
Since the pulley is smooth, the weight of Dwayne Johnson being transferred fully, and pulls the desk with a force of 1157.58 N. The frictional force of the desk is resisting this motion by a force of 370 N. Subtracting both forces we get the resultant force on the desk to be: 1157.58 - 370 = 787.58 N
Now lets use F = ma to calculate for the acceleration of the desk:
787.58 = 63 x acceleration
acceleration = 12.501 m/s
Finally, we can use the motion equation:
here u = 0 m/s (since initial speed of the desk is 0)
a = 12.501 m/s
and s = 10 m
Solving this we get:
Since the desk and Mr. Dwayne Johnson are connected by a taught rope, they are travelling at the same speed. Thus, Dwayne also travels at 15.812 m/s when the desk reaches the window.
