00:01
In this question it is said that there is an electron.
00:04
So electron is moving with velocity.
00:07
That means it is moving with its initial velocity.
00:10
So the velocity is given 5 into 10 cubic meter per second.
00:17
And it enters into a uniform electric field and acquires uniform acceleration.
00:24
So it acquires also the acceleration 10 cube meter per second.
00:30
Square in the direction of its velocity, direction of its motion.
00:35
So u is the initial velocity that the electron is having, and after entering the electric field, it also acquires an acceleration of 10 -meter per second square.
00:46
Now the question is that we have to find out the time in which its velocity will be doubled.
00:53
That means v, the final velocity, will become doubled.
00:58
That is the twice of initial velocity, two times of initial velocity, right? so to you, it means 2 into 5 into 10 cube, that will be 10 into 10 cube, 10 to the power 4 meter per, right? 10 to the power 4 meter per second.
01:19
So it will be the final velocity and at what time its velocity get double that we have to find out.
01:26
So we know the equation of motion, from the equation of motions we can write a is equal to v minus u by t, where a is the acceleration which is already given.
01:44
V minus u is the increase in speed and t is the time duration.
01:50
So now see in this equation a we know that is 10 cube.
01:54
So we will write 10 cube is equal to what is the value of v.
01:58
V is 10 to the power 4.
02:00
So we will write 10 to the power 4.
02:02
What is the value of u? 5 into 10 cube.
02:06
So we will write 5 into 10 cube.
02:08
And the time duration we have to find out.
02:12
So t is equal to 10 cube we will take common.
02:17
So 10 minus 5.
02:19
If we take 10 cube common, so it will remain 10.
02:23
So that 10 cube into 10 will be 10 to the part 4 and minus 5 into 10 cube.
02:29
So it will get adjusted, right? and in the denominator it will come 10 cube.
02:33
So 10 cube, 10 cube will cancel out and it's coming 5.
02:38
And what is the unit of time? the unit of time is second.
02:42
So t is coming 5 .7...