Physics, asked by iimaxsteelii2020, 4 months ago

What is the work done to increase the velocity of a car from 40 km/hr to 60 km/hr if the mass of the car is 1000 kg ? Does the work done by the force have a negative or a positive magnitude ?

Answers

Answered by Ekaro
11

Given :

Initial velocity = 40 km/hr

Final velocity = 60 km/hr

Mass of car = 100 kg

To Find :

Work done by the force.

Solution :

❒ As per work - kinetic energy theorem,

  • Work done = ∆k

» ∆k denotes change in kinetic energy

Kinetic energy of body of mass m moving at a speed of v is given by, k = 1/2 mv²

W = 1/2 m (v² - u²)

  • v denotes final velocity
  • u denotes initial velocity

First of all we need to convert unit of time into m/s. We know that, 1 km/hr = 5/18 m/s

• 40 km/hr = 40 × 5/18 = 11.11 m/s

• 60 km/hr = 60 × 5/18 = 16.67 m/s

By substituting the given values;

➙ W = 1000/2 (16.67² - 11.11²)

➙ W = 500 (277.88 - 123.43)

➙ W = 500 × 154.45

W = 77225 J = 77.2 kJ

❒ Work done by force has a positive magnitude as velocity is increasing with time.

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