A body of mass 5kg rests on a rough horizontal surface of coefficient of friction 0.2. The body is pulled through a distance of 10m by a horizontal force of 25 N. The kinetic energy acquired by it is (g = 10 ms⁻²)

The correct answer is 150 J.

We use the Work-Energy Theorem, which states that the net work done on a body equals the kinetic energy acquired by it (assuming it starts from rest):

\mathrm{KE}=W_{\mathrm{net}}=W_{\mathrm{applied}}-W_{\mathrm{friction}}

Step 1: Identify the given values
Mass, m = 5 kg
Coefficient of kinetic friction, μ = 0.2
Distance, d = 10 m
Applied horizontal force, F = 25 N
g = 10 m/s²

Step 2: Calculate the work done by the applied force

W_{\mathrm{applied}}=F\times d=25\times 10=250\text{J}

Step 3: Calculate the friction force

Since the surface is horizontal, the normal reaction N equals the weight of the body:

N=mg=5\times 10=50\text{N}

f_k=\mu \times N=0.2\times 50=10\text{N}

Step 4: Calculate the work done against friction

Friction acts opposite to the direction of motion, so it does negative work on the body:

W_{\mathrm{friction}}=f_k\times d=10\times 10=100\text{J}

Step 5: Calculate the net kinetic energy acquired

\mathrm{KE}=W_{\mathrm{applied}}-W_{\mathrm{friction}}=250-100=150\text{J}

The kinetic energy acquired by the body is 150 J.