Q. 485.0( 1 Vote )

# A particle of mas

Answer :

**Given:**Mass of the particle : m= 1g = 10

^{-3}kg

Charge of the particle: q = 2.5 × 10

^{–4}C

Electric Field: E = 1.2 × 10

^{4}N C

^{–1}

Distance travelled : s = 40 cm = 0.4 m

Initial velocity: u = 0

**Formula used:**

(a)

When a charge q moves in an uniform electric field E, it experiences an electric force F

_{e}.

F

_{e}= qE

substituting the values we get,

∴ F

_{e}= 3N

Force of gravity would be:

Where m is the mass of the particle and g is the acceleration due to gravity.

Since the mass of the particle is very low, force due to gravity can be neglected.

(b)

From Newton’s Second Law,

F=ma

where a is the acceleration of the body and m is the mass.

acceleration of the particle is:

Here, s is the distance travelled, u is the initial velocity, t is the time required to travel s, and a is the acceleration of the particle.

Substituting we get,

It will take 0.0163 seconds for the particle to travel a distance of 40 cm.

(c)

Using another equation of motion

Here v is the final velocity of the particle,u is the initial velocity of the particle, a is the acceleration and s is the distance travelled by the particle.

Substituting we get,

After travelling 40cm the speed of the particle will be 48.9 m/s.

(d)

We know that,

Work=Force×Displacement

Thus work done by the electric force:

W = F × s

∴ W = 3× 0.4

∴ W = 1.2 J

Hence , work of 1.2 J is being done by the electric force on the particle.

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