A sprinter in a 100-m race accelerates uniformly for the first 71 m and then runs with constant velocity. The sprinter’s time fo
1 answer:
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Answer:
Explanation:
Given that,
When Mass of block is 12kg
M = 12kg
Block falls 3m in 4.6 seconds
When the mass of block is 24kg
M = 24kg
Block falls 3m in 3.1 seconds
The radius of the wheel is 600mm
R = 600mm = 0.6m
We want to find the moment of inertia of the flywheel
Taking moment about point G.
Then,
Clockwise moment = Anticlockwise moment
ΣM_G = Σ(M_G)_eff
M•g•R - Mf = I•α + M•a•R
Relationship between angular acceleration and linear acceleration
a = αR
α = a / R
M•g•R - Mf = I•a / R + M•a•R
Case 1, when y = 3 t = 4.6s
M = 12kg
Using equation of motion
y = ut + ½at², where u = 0m/s
3 = ½a × 4.6²
3 × 2 = 4.6²a
a = 6 / 4.6²
a = 0.284 m/s²
M•g•R - Mf = I•a / R + M•a•R
12 × 9.81 × 0.6 - Mf = I × 0.284/0.6 + 12 × 0.284 × 0.6
70.632 - Mf = 0.4726•I + 2.0448
Re arrange
0.4726•I + Mf = 70.632-2.0448
0.4726•I + Mf = 68.5832 equation 1
Second case
Case 2, when y = 3 t = 3.1s
M= 24kg
Using equation of motion
y = ut + ½at², where u = 0m/s
3 = ½a × 3.1²
3 × 2 = 3.1²a
a = 6 / 3.1²
a = 0.6243 m/s²
M•g•R - Mf = I•a / R + M•a•R
24 × 9.81 × 0.6 - Mf = I × 0.6243/0.6 + 24 × 0.6243 × 0.6
141.264 - Mf = 1.0406•I + 8.99
Re arrange
1.0406•I + Mf = 141.264 - 8.99
1.0406•I + Mf = 132.274 equation 2
Solving equation 1 and 2 simultaneously
Subtract equation 1 from 2,
Then, we have
1.0406•I - 0.4726•I = 132.274 - 68.5832
0.568•I = 63.6908
I = 63.6908 / 0.568
I = 112.13 kgm²
Before we solve this, we should know this fact:
According to Newton's Law of Gravitation, the force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The force acts along the line joining the centres of the two objects. It can be shown by this:
Now, let us check all the options.
A. As we move to higher altitudes, the force of gravity on us decreases.
<em>This </em><em>statement </em><em>is </em><em>true.</em>
The force of gravity is inversely proportional to the square of distance from the centre of the earth. If, we go up the surface of the earth, the distance from the centre of the earth increases and hence the value of force of gravity decrease. So, force of gravity decreases with altitude.
B. As we move to higher altitudes, the force of gravity on us increases.
<em>This </em><em>statement</em><em> </em><em>is </em><em>false.</em>
We have already got the result in option A. that the force of gravity decreases with altitude. It never increases with altitude.
C. As we gain mass, the force of gravity on us decreases.
<em>This </em><em>statement</em><em> </em><em>is </em><em>false.</em>
The force of gravity is directly proportional to the product of the masses. So, if increase our mass, then the force of gravity will also increase and if we decrease our mass, then the force of gravity decreases.
D. As we gain mass, the force of gravity on us increases.
<em>This </em><em>statement</em><em> is</em><em> </em><em>true.</em>
As mentioned earlier in option C., the force of gravity is directly proportional to the product of the masses of the earth and another object. So, as we gain mass, the force of gravity on us increases.
E. As we move faster, the force of gravity on us increases.
<em>This </em><em>statement</em><em> is</em><em> </em><em>true</em><em>.</em>
Here, we have to consider a different formula. According to Newton's Second Law,
F = ma, where F is the force, m is the mass and a is the acceleration.
In other words,
F ∝ a, i.e., force is directly proportional to acceleration.
We know, acceleration is the rate of change of velocity of an body within a time period.
So, if speed is increased, then acceleration will also be greater, which results in the increase of force. So, as we move faster, the force of gravity on us increases.
<u>Answers:</u>
A: As we move to higher altitudes, the force of gravity on us decreases.
D: As we gain mass, the force of gravity on us increases.
E: As we move faster, the force of gravity on us increases.
Hope you could understand.
If you have any query, feel free to ask.