A)♣ the string being pulled,
<span>the angular speed is: w1=w0 +w’*t, hence t=(w1-w0)/w’; </span>
<span>the angular path is: b=w0*t+0.5*w’*t^2, where angular acceleration </span>
<span>w’=T/J, torq T=F*r, and b*r=L; </span>
<span>♦ thus b=w0*(w1-w0)/w’ +0.5*w’*((w1-w0)/w’)^2 = </span>
<span>= (w1-w0)*(w0 +0.5w1 -0.5w0)/w’ =0.5*(w1^2 –w0^2)/w’; </span>
<span>♠ and b=L/r =0.5*(w1^2 –w0^2)/(F*r/J); </span>
<span>2(F*r/J)*L/r =w1^2 –w0^2, hence </span>
<span>w1^2=2F*L/J +w0^2; </span>
<span>b)♣ the power is P=F*(w0*r);
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Explanation:
KE is directly proportional to the square of velocity / speed.
if speed is 2 times (doubled) the KE will be
= 4 times the original KE
Answer:
D. The ice-to-liquid phase change of water requires less energy than the liquid-to-vapor phase.
Explanation:
In the phase change from liquid to gas, the bonds between atoms are completely broken. The phase change from liquid to gas requires more energy because the bonds must be completely broken for it to take place, rather than just loosened as in the phase change of solid to liquid.
Phase changes can have a strong stabilizing effect on temperatures that are not near the melting and boiling points, since evaporation and condensation occur even at temperatures below the boiling point.
More energy is required to evaporate water below the boiling point than at the boiling point, because the kinetic energy of water molecules at temperatures below 100°C is less than that at 100°C, so less energy is available from random thermal motions.
Answer:
3.16X10∧-11 m
Explanation:
1/2 mv2 = qV (KE = Electric potential energy)
velocity = √2qV/m = √( 2X 1.6X10∧-19 X 1500/9.11X10∧-31)
2.3X10∧7m/s
now use De Broglie equation
λ = h/mv
= 6.62X10∧-34/( 9.11X10∧-31 X 2.3X10∧7)
3.16 X 10∧-11 m
or
use the above equations and substitute to get the final eqiation
λ = h/√(2mqV) = 3.16X 10∧-11 m
the position that has least kinetic energy is option D
