Two wires are parallel and one is directly above the other. Each has a length of 50.0 m and a mass per unit length of 0.020 kg/m
2 answers:
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Answer:
1) 3.66 s
2) 124.44 m
3) 3.12 s
Explanation:
Let's start by first listing down the information in the question.
Red Car : 34 m/s
Blue Car: 28 m/s
Distance between them : 22 m
The difference in speed between the cars is: 34 - 28 = 6 m/s
This means that the red car is catching up to the blue car at a speed of 6 m/s.
1) We can solve this by just dividing the distance by the difference in speed. This becomes:
Thus it takes 3.66 seconds for the red car to catch up to the blue car.
2) We know from (1) that it took 3.66 seconds for the red car to catch up. Since the speed it was travelling at is constant, we only need to multiply it by the time from (1) to get the distance.
This becomes:
Thus the red car travels 124.44 m before catching up to the blue car.
3) If the red car starts to accelerate the moment we see it, the time taken to get to the blue car will be less than before. We can find this in a simple way.
We can use the motion equation :
Here s = 22 m
We can take u as the difference in speed. u = 6 m/s
Acceleration a = (2/3) m/s^2
Substituting the these into the equation we get:
Solving this for the variable 't' using the quadratic formula we get the following two answers:
t1 = 3.12 s
t2 = - 21.12 s
Since t2 is not possible, the answer is t1. This means it takes 3.12 seconds for the red car to catch up to the blue.
(a) 5.69 N/C, vertically downward
We can calculate the acceleration of the electron by using the SUVAT equation:
where
d = 4.50 m is the distance travelled by the electron
u = 0 is the initial velocity of the electron
is the time of travelling
a is the acceleration
Solving for a,
Given the mass of the electron,
We can find the electric force acting on the electron:
And the electric force can be written as
where
is the charge of the electron
E is the magnitude of the electric field
Solving for E,
The negative sign means that the direction of the electric field is opposite to the direction of the force (because the charge is negative): since the force has same direction of the acceleration (vertically upward), the electric field must point vertically downward.
(b) Yes
We can answer the question by calculating the magnitude of the gravitational force acting on the electron, to check if it is relevant or not. The gravitational force on the electron is:
where
is the mass of the electron
is the acceleration due to gravity
Substituting,
We see that the gravitational force is basically negligible compared to the electric force calculated in part (a), therefore we can say it is justified to ignore the effect of gravity in the problem.