Objects should be cooled before their mass is determined on a sensitive balance because it could damage the balance. Also, because it would give you wrong reading of the mass. Hot objects would warm the air around it. A warm air would expand and would produce convection as it rises causing to give the object a mass that is less than the actual. Another reason would be it would cause instability in the readings, the mass would fluctuate every now and then due to the convection currents around the object. It is always recommended to weigh the masses of objects that are in room temperature.
Answer:
8.91 J
Explanation:
mass, m = 8.20 kg
radius, r = 0.22 m
Moment of inertia of the shell, I = 2/3 mr^2
= 2/3 x 8.2 x 0.22 x 0.22 = 0.265 kgm^2
n = 6 revolutions
Angular displacement, θ = 6 x 2 x π = 37.68 rad
angular acceleration, α = 0.890 rad/s^2
initial angular velocity, ωo = 0 rad/s
Let the final angular velocity is ω.
Use third equation of motion
ω² = ωo² + 2αθ
ω² = 0 + 2 x 0.890 x 37.68
ω = 8.2 rad/s
Kinetic energy,

K = 0.5 x 0.265 x 8.2 x 8.2
K = 8.91 J
Light will make the object appear “broken” or in an irregular shape.
Refraction is the change in direction of waves.
Answer:
55000000 years
Explanation:
Rate of North American Plate moving (Velocity) = 20 mm/yr
Degrees New York has to move = 10° west
New York's longitude = 110 km/°
Distance of New York = 110×10 = 1100 km
= 1100×10⁶ mm

∴ Time taken by New York to move 10° west is 55000000 years