Question

what will be the work done to stop moving cycle of mass 30kg which is moving with speed 54km per hour

Answer 1

Based on Work - Energy Principle :

The Change in the Kinetic Energy of the Cycle is equal to the Net Work done on the Object.

$W_n_e_t = \frac{mv^2}{2} - \frac{mu^2}{2}$

Where u is the initial velocity and v is the final velocity

Given the mass of the Cycle = 30 kg

Intial Velocity (u) = 54km/hr = 54000/3600 = 15m/sec

Final Velocity (v) = 0 (because we are stopping the cycle)

Substituting all the values in our Net Work done Equation we get :

⇒ Work done to stop the Cycle = 0 - (30 × 15²)/2 = -15³ = -3375 Joules

(Negative sign show's that We are doing Work on the Cycle to stop it)