This drag force is always opposite to the object's motion, and unlike friction between solid surfaces, the drag force increases as the object moves faster.
Answer:
(a) 
(b) P = 0.816 Watt
Explanation:
(a)
The power radiated from a black body is given by Stefan Boltzman Law:

where,
P = Energy Radiated per Second = ?
σ = stefan boltzman constant = 5.67 x 10⁻⁸ W/m².K⁴
T = Absolute Temperature
So the ratio of power at 250 K to the power at 2000 K is given as:

(b)
Now, for 90% radiator blackbody at 2000 K:

<u>P = 0.816 Watt</u>
Answer:
See the answer below
Explanation:
1. Speed is calculated as the ratio of distance and time. Hence, Jame's speed can be calculated as:
400/5 km/hr = 80 km/hr
The unit for the speed would be km/hr. This can also be converted to m/s:
80 km = 80,000 m
1 hr = 3,600 s
80 km/hr = 80,000/3600 m/s = 22.22 m/s
2. Since James drove 400 km in 5 hours, the distance he drove is 400 km.
3. The time it took for James to get there is 5 hours.
Yes. On a circular path, the direction of motion is constantly changing. Change of direction is acceleration, even at constant speed.
1) D
2) I would say A, but not 100%, its the only one that makes sense tho