Question

An electron travelling with the speed 5 × 10^3 m s^-1 passes through an electric Field with acceleration 10^12 m s^-2. how long will it take to double its speed ? ( Chapter- motion in straight line )​

Answer 1

Given:-

→ Initial velocity of the electron (u)

= 5×10³ m/s

→ Acceleration (a) = 10¹² m/s²

To find:-

→ Time taken by the electron to double

it's speed.

Solution:-

In this case :-

• Final velocity [v] of the electron will be double of the initial velocity i.e. 2u.

Let's calculate the required time by using the 1st equation of motion :-

=> v = u + at

Where:-

• v is final velocity of the body.

• u is initial velocity of the body.

• a is acceleartion of the body.

• t is time taken.

=> 2u = u + at

=> 2u - u = at

=> u = at

=> t = u/a ---(1)

By substituting values in eq.1,we get:-

=> t = 5×10³/10¹²

=> t = 5×10³⁻¹²

=> t = 5×10⁻⁹ s

Thus, the electron will take

5×10⁻⁹ seconds to double it's speed.