The same girl in number 3 (above) pushes another friend on the same skateboard.
1 answer:
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Answer:
0.087 m
Explanation:
Length of the rod, L = 1.5 m
Let the mass of the rod is m and d is the distance between the pivot point and the centre of mass.
time period, T = 3 s
the formula for the time period of the pendulum is given by
.... (1)
where, I is the moment of inertia of the rod about the pivot point and g is the acceleration due to gravity.
Moment of inertia of the rod about the centre of mass, Ic = mL²/12
By using the parallel axis theorem, the moment of inertia of the rod about the pivot is
I = Ic + md²
Substituting the values in equation (1)
12d² -26.84 d + 2.25 = 0
d = 2.15 m , 0.087 m
d cannot be more than L/2, so the value of d is 0.087 m.
Thus, the distance between the pivot and the centre of mass of the rod is 0.087 m.
Answer:
Energy required = 3169.34 Joules.
Explanation:
The quantity of energy (Q) required can be determined by;
Q = mcΔθ
Where: m is the mass, c is the specific heat and Δθ is the change in temperature.
But, m = 96.7 kg, c = 0.874 J/(kg),
=
and
=
.
So that,
Q = mc( -
)
= 96.7 x 0.874 x ( -
)
= 96.7 x 0.874 x 37.5
= 3169.3425
Q = 3169.34
= 3.2 KJ
The amount of energy required is 3169.34 Joules.