Answer:
Explanation:
Work done in lifting the weight once = mgh
= 20 x 9.8 x (1.9+1.7)
= 705.6 J
= 705.6 / 4.2 calorie
= 168 cals
Total energy to be spent = 600 x 10³ cals
No of times weight is required to be lifted
= 600 x 10³ / 168
= 3.57 x 10³ times
Total time to be taken = 2 x 3.57 x 10³
= 7.14 x 10³ s
=119 minutes .
Answer:

Explanation:
MA ( Mechanical Advantage ) is always less than VR ( Velocity Ratio ) because <u>MA</u><u> </u><u>is</u><u> </u><u>reduced</u><u> </u><u>by</u><u> </u><u>friction</u><u> </u><u>but</u><u> </u><u>VR</u><u> </u><u>is</u><u> </u><u>not</u><u> </u><u>affected</u><u> </u><u>by</u><u> </u><u>friction</u><u>.</u>
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<span>C is the correct answer. Electron microscopes require a vacuum to work, so living cells cannot be seen because they cannot respire. Light microscopes use a ray of visible light instead of a beam of electrons to magnify something so it can be seen by the naked eye. There are two different types of electron microscope: transmission (TEM) and scanning (SEM).</span>
The answer should be c....
Answer:
a) Ktotal = 71.85 J
b) Ktotal = 71.85 J
Explanation:
a) The total kinetic energy is that of the total mass of the bicycle plus the rotational kinetic energy of the two wheels. The linear speed of the circumference of the wheels matches the forward speed of the bicycle, so their angular speed is
ω = v/r
The moment of inertia of one solid disk bicycle wheel is
I = 0.5*m₂*r²
And the rotational kinetic energy of one wheel is
Kr = 0.5*I*ω² = 0.5*(0.5*m₂*r²)*(v/r)² = 0.25*m₂*v²
The total kinetic energy is then that of the frame and wheels plus the rotational kinetic energy.
Ktotal = 0.5*(m₁ + 2*m₂)*v² + 2*(0.25*m₂*v²)
⇒ Ktotal = 0.5*v²*(m₁ + 3*m₂)
where
m₁ = 6.75 Kg
m₂ = 0.820 kg
v = 3.95 m/s
then
⇒ Ktotal = 0.5*(3.95 m/s)²*(6.75 Kg + 3*0.820 kg)
⇒ Ktotal = 71.85 J
b) We can apply the same equation obtained before
⇒ Ktotal = 0.5*v²*(m₁ + 3*m₂)
where
m₁ = 675 Kg
m₂ = 82.0 kg
v = 0.395 m/s
then
⇒ Ktotal = 0.5*(0.395 m/s)²*(675 Kg + 3*82 kg)
⇒ Ktotal = 71.85 J