Answer:
B.
It will be greater than 10 J.
Explanation:
The total mechanical energy of an object is the sum of its potential energy (PE) and its kinetic energy (KE):
E = PE + KE
According to the law of conservation of energy, when there are no frictional forces on an object, its mechanical energy is conserved.
The potential energy PE is the energy due to the position of the object: the highest the object above the ground, the highest its PE.
The kinetic energy KE is the energy due to the motion of the object: the highest its speed, the largest its KE.
Here at the beginning, when it is at the top of the roof, the baseball has:
PE = 120 J
KE = 10 J
So the total energy is
E = 120 + 10 = 130 J
As the ball falls down, its potential energy decreases, since its height decreases; as a result, since the total energy must remain constant, its kinetic energy increases (as its speed increases).
Therefore, when the ball reaches the ground, its kinetic energy must be greater than 10 J.
no, work is = force * distance or displacement
Answer:
4 smaller disks
Explanation:
We are given;
Mass of smaller and larger disks = M
Radius of smaller disk = R
Radius of larger disk = 4R
Formula for moment of inertia about cylinder axis is:
I = ½MR²
Thus;
For small disk, I_small = ½MR²
For large disk, I_large = ½M(2R)² = 2MR²
We are told that moment of inertia of System A consists of two of the larger disks. Thus;
I_A = 2 × I_large = 2 × 2MR²
I_A = 4MR²
We are also told that System B consists of one of the larger disks and a number of the smaller disks. Thus;
I_B = I_large + n(I_small)
Where n is the number of smaller disks.
I_B = 2MR² + n(½MR²)
I_B = MR²(2 + n/2)
We are told that the moment of inertia for system A equals the moment of inertia for system B. Thus;
I_A = I_B
So;
4MR² = MR²(2 + n/2)
MR² will cancel out to give;
4 = 2 + n/2
Multiply through by 2 to give;
8 = 4 + n
n = 8 - 4
n = 4
Answer:
Option C
Maximum potential energy is at point R.
Explanation:
Potential energy is a product of mass, acceleration due to gravity and height ie
PE=mgh where PE is the potential energy, m is mass of an object, g is acceleration due to gravity whose value is normally taken as 9.81 and h is height. Since at point R we have the maximum height, the potential energy will be highest at this point.
Answer: Remember speed is distance divided by time, so if he travels 1000 m in 7.045 s, his speed is
(1000 m)/(7.045 s) = 141.9 m/s.
Note there are 1609 metres in a mile, or 1 mi = 1609 m, so m = 1/1609 mi, or
141.9/1609 mi/s = 0.08822 mi/s. Now, note that 1 h = 3600 s, so the speed is
0.08822*3600 mi/h = 317.6 mi/h.
