The crane does NO work.
Work = (force) x (distance)
= (1,000 N) x (150 meters ?) = 150,000 joules
But the work is in the direction of the force, and it isn't the crane
pushing the material down. It's gravity.
Gravity is doing the work.
If the material was being lowered by a cable wrapped around the shaft
of an electric generator, then you could use the work done by gravity to
generate some electrical energy, and then sell the energy.
Or, if the "material" happened to be water, you could let gravity lower it
through a turbine or a water wheel, and use the work done by gravity to
grind wheat.
Yes, the crane may be raising a sweat, working against gravity. The
purpose is only to prevent gravity from doing the work too fast.
Answer:
(a) Workdone = -27601.9J
(b) Average required power = 1314.4W
Explanation:
Mass of hoop,m =40kg
Radius of hoop, r=0.810m
Initial angular velocity Winitial=438rev/min
Wfinal=0
t= 21.0s
Rotation inertia of the hoop around its central axis I= mr²
I= 40 ×0.810²
I=26.24kg.m²
The change in kinetic energy =K. E final - K. E initail
Change in K. E =1/2I(Wfinal² -Winitial²)
Change in K. E = 1/2 ×26.24[0-(438×2π/60)²]
Change in K. E= -27601.9J
(a) Change in Kinetic energy = Workdone
W= 27601.9J( since work is done on hook)
(b) average required power = W/t
=27601.9/21 =1314.4W
Answer:
a) 1.725*10^5 N
b) 3.83*10^3 N
c) i) 173.24 kN
c) ii) 4.57 kN
Explanation:
See the attachment for calculations
Answer:
compared to the incident angle, the refracted angle is 45.56⁰
Explanation:
From Snell's law;
n₁sin(I) = n₂sin(r)
Where;
n₁ is the refractive index of light in medium 1 = 1.2
n₂ is the refractive index of light in medium 2 = 1.4
I is the incident angle
r is the refractive angle
I = 56.439⁰
Applying snell's law
Therefore, compared to the incident angle, the refracted angle is 45.56⁰
Answer:
Torque; τ = 4.712 × 10^(-3) J
Magnetic moment; M = 0.0248 J/T
Explanation:
Torque is gotten from the formula;
τ = BIA
Where;
B is magnetic field
I is current
A is area
We are given;
B = 0.19T
I = 6.2A
Rectangle dimensions = 5cm by 8cm = 0.05m by 0.08m
Thus;
Area; A = 0.05m × 0.08m = 0.004 m²
Thus;
τ = 0.19 × 6.2 × 0.004
τ = 4.712 × 10^(-3) J
Formula for the magnetic moment is given by;
M = IA
M = 6.2 × 0.004
M = 0.0248 J/T
