According to the conservation of mechanical energy, the kinetic energy just before the ball strikes the ground is equal to the potential energy just before it fell.
Therefore, we can say KE = PE
We know that PE = m·g·h
Which means KE = m·g·h
We can solve for h:
h = KE / m·g
= 20 / (0.15 · 9.8)
= 13.6m
The correct answer is: the ball has fallen from a height of 13.6m.
Answer:
Final angular velocity is 35rpm
Explanation:
Angular velocity is given by the equation:
I1w1i + I2w2i = I1w1f -I2w2f
But the two disks are identical, so Ii =I2
wf can be calculated using
wf = w1i - w2i/2
Given: w1i =50rpm w2i= 30rpm
wf= (50 + 20) / 2
wf= 70/2 = 35rpm
When the child is moving, he/she has kinetic energy. For just a brief second before they move the other way, the child is not moving, but they have gravitational potential energy.
The child may need a push from time to time because friction with the air causes loss of energy.
Water is treated by purifying it by adding slaked lime or potash alum
Answer: T= 715 N
Explanation:
The only external force (neglecting gravity) acting on the swinging mass, is the centripetal force, which. in this case, is represented by the tension in the string, so we can say:
T = mv² / r
At the moment that the mass be released, it wil continue moving in a straight line at the same tangential speed that it had just an instant before, which is the same speed included in the centripetal force expression.
So the kinetic energy will be the following:
K = 1/2 m v² = 15. 0 J
Solving for v², and replacing in the expression for T:
T = 1.9 Kg (3.97)² m²/s² / 0.042 m = 715 N