Work, Energy and Power

• A 500 N object is lifted 2.2 m in 2 s.

Work Calculation

• Work is force times distance.
• The work done in lifting the object is 1100 Joules (500 N * 2.2 m).

Potential Energy

• Potential Energy (PE) is force times height.
• The potential energy of the barbell when lifted is 1100 Joules (500 N * 2.2 m).

Power Calculation

• Power is work divided by time.
• The power expended is 550 Watts (1100 J / 2 s).

Specific Heat

• Specific heat is the energy needed to raise the temperature of 1 g of a substance by 1 °C.

Power Defined

• Power is defined as the rate at which energy is transferred.

Elastic Collision Examples

• Billiard balls bouncing off each other exemplify elastic collision.
• Air molecules colliding in a balloon represent an elastic collision.
• A superball hitting the ground and rebounding demonstrates elastic collision.

Inelastic Collision Examples

• A car crash where vehicles stick together is an example of an inelastic collision.
• A lump of clay hitting the floor and flattening demonstrates inelastic collision.
• Two football players colliding and falling to the ground represent an inelastic collision.

Law of Conservation of Energy

• Energy keeps changing in an isolated system.

Pendulum Kinetic Energy

• Position C has the highest kinetic energy as it's the lowest point with maximum speed.

Pendulum Potential Energy

• Position C has the lowest potential energy because it is closest to the ground.
• Positions A and E have the highest potential energy; they are the pendulum's highest points where it momentarily rests.

Object Falling

• When an object falls, its kinetic energy increases, and potential energy decreases.

Object Thrown Upward

• When an object is thrown upward, its kinetic energy decreases.

Matching Units with Physical Quantities

• kg⋅m/s corresponds to Momentum.
• J/kg⋅°C corresponds to Specific heat.
• N⋅m corresponds to Work, also known as torque.
• W (Watt) corresponds to Power.
• Joule corresponds to Heat energy, Kinetic energy, or Potential energy.
• kWh (kilowatt-hour) corresponds to Heat energy or any form of energy.
• kg⋅m²/s² corresponds to Kinetic energy or Potential energy.
• Pascal corresponds to Pressure.

Work Calculation for a Man Climbing Stairs

• A 70 kg man climbs to a height of 16 m.
• Gravitational acceleration (g) is 9.8 m/s².
• Work done is 10,976 Joules (70 kg * 9.8 m/s² * 16 m).

Power Calculation for a Man Climbing Stairs

• The man climbs the stairs in 25 s.
• Power is 439.04 Watts (10,976 Joules / 25 s).

Increasing Power

• Power can be increased by decreasing weight.

Density and Buoyancy: Cubic Object

• A 10-g cubic object has a side of 3 cm.
• The volume of the object is 27 mL (3^3 cm³).
• The density is approximately 0.37 g/mL (10 g / 27 mL).
• The object will float because its density is less than water's density (1 g/mL).

Density and Buoyancy: Displaced Volume

• A 10-g object displaces 5 mL of water.
• The object's volume is 5 mL.
• The density is 2 g/mL (10 g / 5 mL).
• The object will sink because its density is greater than water's density.

Buoyant Force

• The buoyant force of a liquid equals the weight of the displaced liquid.

Work-Energy Theorem

• The Work-Energy Theorem states that total work done equals change in kinetic energy.

Momentum Change

• The change in momentum is equal to Impulse.

Total Work Calculation from a Graph

• Three sections make up graph:
• From 0 to 5 m: triangle; base = 5 m, height = 3 N, area = 7.5 J.
• From 5 to 10 m: rectangle; width = 5 m, height = 3 N, area = 15 J.
• From 10 to 15 m: triangle; base = 5 m, height = 3 N, area = 7.5 J.
• Total work done: 30 J (7.5 J + 15 J + 7.5 J).