A charged particle of q =1C and mass m =1kg accelerates in a uniform electric fi

Question

A charged particle of q=1C and mass m=1kg accelerates in a uniform electric field of strength E=5 N/C.   What is the particle's acceleration?

1/5 m/s2

3 m/s2

5 m/s2

10 m/s2

0 m/s2

1kg of a certain liquid substance freezes at -35 degrees Celcius. If the liquid starts at an initial temperature of 45 degrees Celcius, find the heat transferred to produce a solid at -50 degrees Celcius. The heat must have the appropriate sign relative to the substance.

Use the following constants to solve the problem:

Specific heat of the liquid cl= 1J/kgK
Specific heat of the solid cs= 2J/kgK
Latent heat of fusion Lf=10J/kg

-120J

-255J

222J

-110J

-80J

1/5 m/s2

3 m/s2

5 m/s2

10 m/s2

0 m/s2

Explanation / Answer

1)
Charge, q = 1C
Electric field, E = 5 N/C
Force, F = qE = 5 N
Acceleration = F/m
= 5/1
= 5 m/s2

2)
First the liquid cool down from 45 degrees ot -35 degrees, then changes from liquid to solid at -35 degrees, further cools to -50 degrees.
i)
Heat transferred when cooling from 45 to -35 degrees
Q1 = m x Cl x dT
= 1 x 1 x (-35 - 45)
= - 80 J
ii)
Heat transferred for change of state from liquid to solid
Q2 = - m x Lf
= - 1 x 10 = - 10 J
iii)
Heat released when the substance cools down from - 35 to - 50 degrees
Q3 = m x Cs x dT
= 1 x 2 x [- 50 - (-35)]
= - 30 J
Total heat = Q1 + Q2 + Q3
= - 80 - 10 - 30
= - 120 J

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