Answer:
Explanation:
The rate at which heat will be radiated is given by the expression
E = e Aσ ( T⁴ - T₀⁴ )
E is heat radiated , e is emissivity , A is area of surface , σ is stephan's constant T is temperature of the object and T₀ is temperature of the surrounding .
For all the objects given , e , σ T and T₀ are same so E will solely dependent on area of the surface
surface area of cube= 6 r² ,
surface area of sphere = 4 π r²
= 12.56 r²
hemisphere = 2 π r²
= 6.28 r²
12.56 r² >6.28 r² > 6 r²
heat radiated by sphere > heat radiated by hemisphere > heat radiated by cube .
Answer:
A. 39.2 m/s
B. 78.4 m
Explanation:
Data obtained from the question include:
Time (t) = 4 s
Acceleration due to gravity (g) = 9.8 m/s²
A. Determination of the brick's velocity.
Time (t) = 4 s
Acceleration due to gravity (g) = 9.8 m/s²
Velocity (v) =?
v = gt
v = 4 × 9.8
v = 39.2 m/s
Thus, the brick's velocity after 4 s is 39.2 m/s
B. Determination of how far the brick fall in 4 s.
Time (t) = 4 s
Acceleration due to gravity (g) = 9.8 m/s²
Height (h) =?
h = ½gt²
h = ½ × 9.8 × 4²
h = 4.9 × 16
h = 78.4 m
Thus, the brick fall 78.4 m during the time.
Answer: c. 4.56 × 105 J
Explanation:
Given that
mass of lead brick, m= 7.25kg
Temperature T1 = 18.0 °C
Temperature T2 = 328 °C
specific heat capacity of lead, c = 128 J/(kg∙C°)
latent heat of fusion Lfusion =23,200 J/kg
Amount of energy Q =?
Using the formulae
Amount of energy ,Q =mc ( T2-T1)+ mLfusion
7.25kg x 128 J/(kg∙C°) x (328-18°C) + 7.25kg x 23200 J/kg
=455880J
=4.56 x 10^5 J
Weight of the carriage 
Normal force 
Frictional force 
Acceleration 
Explanation:
We have to look into the FBD of the carriage.
Horizontal forces and Vertical forces separately.
To calculate Weight we know that both the mass of the baby and the carriage will be added.
- So Weight(W)

To calculate normal force we have to look upon the vertical component of forces, as Normal force is acting vertically.We have weight which is a downward force along with
, force of
acting vertically downward.Both are downward and Normal is upward so Normal force 
- Normal force (N)

- Frictional force (f)

To calculate acceleration we will use Newtons second law.
That is Force is product of mass and acceleration.
We can see in the diagram that
and
component of forces.
So Fnet = Fy(Horizontal) - f(friction) 
- Acceleration (a) =

So we have the weight of the carriage, normal force,frictional force and acceleration.