Question

A force act on a body of mass 5 kg causing its speed to increase from 4 m/s to 6 m/s. How much work has the force done?​

Answer 1

Answer:

50 Joules

Explanation:

First we will list the things given in the question.

We are given-

1. Mass (m) = 5Kg

2. Initial Velocity (u) = 4m/s

2. Initial Velocity (u) = 4m/s3. Final velocity (v) = 6m/s

From Newton's second law of motion-

F = ma

First, let us find the acceleration of the object as we need it to find the force applied. We know that-

$a = \frac{(v - u)}{t}$

Therefore

$a = \frac{6 - 4}{t} = \frac{2}{t}$

Therefore Force will be

$5 \times \frac{2}{t} = \frac{10}{t} \: newtons$

Now to find total work done, we apply its formula

$w = f \times s$

We need to find distance (s) here first.

From third kinematic equation of motion-

${v}^{2} = 2as + {u}^{2} \\ > {6}^{2} = 2 \times \frac{2}{t} \times s + {4}^{2} \\ > 36 = \frac{4s}{t} + 16 \\ > 20 = \frac{4s}{t} \\ or \: s = 5t$

Okay, now we have force acting and distance too, we just need to put these values in our work formula.

$w = \frac{10}{t} \times 5t \\ > 50$

Therefore, work done by the force is 50 Joules.