Answer:
14 seconds
Explanation:
Distance covered by sports car is measured with 21*t where t is time.
Distance covered by police is measured with at^2/2(t-time, a-acceleration) as it doesnt have starting velocity. If the distances are equal(police catches sport car)
then we have 21t=3/2*t^2 Solving this equation we get t=14 & t=0;
excluding the starting point we have 14 seconds
Answer:
f =-20 cm
Explanation:
Given that,
The magnification of a spherical mirror, m = -1
The image distance, v = 40 cm (for negative magnification)
The magnification of a concave mirror is negative. The mirror showing -1 magnification is a concave mirror.
Let f be the focal length of the mirror. We know that,
Object distance, u = -40 cm
Using mirror's formula i.e.
So, the focal length of the mirror is 20 cm.
Answer:
32%
Explanation:
For a heat engine, efficiency is work out divided by heat in:
η = Wₒ / Qᵢ
Since energy is balanced, heat in is the sum of work out and heat out:
Qᵢ = Wₒ + Qₒ
Therefore:
η = Wₒ / (Wₒ + Qₒ)
Given Wₒ = 710 J and Qₒ = 1480 J:
η = 710 / (710 + 1480)
η = 0.32
The thermal efficiency is 32%.
I took this test before, aren't there answer choices? :)
