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)