C. element only one substance
<h2>
The answer got is reasonable.</h2>
Explanation:
We have equation of motion v² = u² + 2as
Initial velocity, u = 300 m/s
Acceleration, a = ?
Final velocity, v = 400 m/s
Displacement,s = 4 km = 4000 m
Substituting
v² = u² + 2as
400² = 300² + 2 x a x 4000
a = 8.75 m/s² = 8.8 m/s²
The acceleration is 8.8 m/s²
The answer got is reasonable.
Answer:
instantaneous velocity is a velocity covered at an instant while average velocity is the change in distance/ the change in time taken
If it produces 20J of light energy in a second, then that 20J is the 10% of the supply that becomes useful output.
20 J/s = 10% of Supply
20 J/s = (0.1) x (Supply)
Divide each side by 0.1:
Supply = (20 J/s) / (0.1)
<em>Supply = 200 J/s </em>(200 watts)
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Here's something to think about: What could you do to make the lamp more efficient ? Answer: Use it for a heater !
If you use it for a heater, then the HEAT is the 'useful' part, and the light is the part that you really don't care about. Suddenly ... bada-boom ... the lamp is 90% efficient !
