A motorist travels for 3.0 h at 80 km/h and 2.0 h at 100 km/h. What is her average speed for the trip?
2 answers:
Answer:
The motorist average speed for the trip is 88 km/h
Explanation:
In order to know her average speed, we have to refer to the following ecuation:
<V> (average speed) =
So, according to that, we know that the motorist has been having a speed of 80km/h during 3 hours, and a speed of 100 km/h during 2 hours. It means that her speed during all the travel is 5 hours.
Then, we have to affect the 5 hours to the inicial and final speed as follows:
First, at 80 km/h, she travels during 2 hours so:
3h*80km/h= 240 km
And then, at 100 km/h:
2h*100km/h= 200 km
Which leads us to:
initial speed: 240 km/ 5 h= 48 km/h
and final speed of: 200 km/ 5 h= 40 km/h
Then, the average speed is:
<V> = 48 km/h + 40 km/h = 88 km/h
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Answer: 39.8 μC
Explanation:
The magnitude of the electric field generated by a capacitor is given by:
d is the distance between the plates.
For a capacitor, charge Q = CV where C is the capacitance and V is the voltage.
where A is the area of the plate and ε₀ is the absolute permittivity.
substituting, we get
It is given that the magnitude of the electric field that can exist in the capacitor before air breaks down is, E = 3 × 10⁶ N/C.
radius of the plates of the capacitor, r = 69 cm = 0.69 m
Area of the plates, A = πr² = 1.5 m²
Thus, the maximum charge that can be placed on disks without a spark is:
Q = E×ε₀×A
⇒ Q = 3 × 10⁶ N/C × 8.85 × 10⁻¹² F/m × 1.5 m² = 39.8 × 10⁻⁶ C = 39.8 μC.