### Shortcut Methods

**Shortcut Methods and Tricks to Solve Numericals**

**1. Work Done by a Force**

- Work done = Force * displacement in the direction of the force.

**2. Potential Energy**

- Potential energy = mass * gravity * height.

**3. Kinetic Energy**

- Kinetic energy = 1/2 * mass * velocity^2.

**4. Power Output of a Motor**

- Power output = Work done / Time taken.

**5. Electrical Energy Consumed by a Light Bulb**

- Electrical energy consumed = Power * Time.

**6. Heat Energy Generated by a Heater**

- Heat energy generated = Power * Time.

**Examples of Shortcut Methods Applied**

**1.** A 20 kg body is acted upon by a force of 10 N. Calculate the work done by the force when the displacement is 5 m.

Work done = Force x displacement Work done = 10 N x 5 m Work done = 50 J

**2.** A 50 kg block is lifted vertically through a height of 10 m. Calculate the potential energy gained by the block.

Potential energy = mass x gravity x height Potential energy = 50 kg x 9.8 m/s^2 x 10 m Potential energy = 4900 J

**3.** A body of mass 10 kg is moving at a speed of 10 m/s. Calculate the kinetic energy of the body.

Kinetic energy = 1/2 x mass x velocity^2 Kinetic energy = 1/2 x 10 kg x 10^2 m/s^2 Kinetic energy = 500 J

**4.** A 5 kW motor lifts a load of 100 kg through a height of 20 m in 10 s. Calculate the power output of the motor.

Power output = Work done / Time taken Power output = (100 kg x 9.8 m/s^2 x 20 m) / 10 s Power output = 19.6 kW

**5.** A 100 W light bulb is left on for 10 hours. Calculate the electrical energy consumed.

Electrical energy consumed = Power x Time Electrical energy consumed = 100 W x 10 h Electrical energy consumed = 1 kilowatt-hours (kWh)

**6.** A 2 kW electric heater is used to heat water for 30 minutes. Calculate the amount of heat energy generated.

Heat energy generated = Power x Time Heat energy generated = 2 kW x 30 min Heat energy generated = 1 kilowatt-hours (kWh)