Physics Chapter: Effects of Gravity and Motion

Effects of Gravity

• Without gravity, objects would float freely, including the atmosphere and oceans.
• Life as we know it would be impossible, as gravity keeps us grounded and helps maintain the Earth's atmosphere.

Center of Gravity

• The center of gravity is the point where the weight of an object is concentrated.
• Examples:
  • A seesaw balanced perfectly, with the center of gravity directly above the fulcrum.
  • A gymnast performing a handstand, their center of gravity aligned over their hands.

Circular Motion

• A stone tied to a string and whirled in a circle exhibits uniform circular motion.
• The stone's path is a circle.
• The stone's speed is constant, but its velocity changes due to the change in direction.
• Daily life examples:
  • Swinging a pendulum
  • A car turning a corner
  • A planet orbiting a star

Calculating Weight

• Weight is the force exerted on an object due to gravity.
• Equation: Weight (W) = Mass (m) * Acceleration due to gravity (g)
• Given mass (m) = 60 kg and acceleration due to gravity (g) = 10 m/s²
• Therefore, weight (W) = 60 kg * 10 m/s² = 600 Newtons (N)

Projectile Motion

• A ball projected vertically upward experiences projectile motion.
• Equation for maximum height (H) = (initial velocity (v)²) / (2 * acceleration due to gravity (g))
• Given initial velocity (v) = 100 m/s and acceleration due to gravity (g) = 10 m/s²
• Therefore, maximum height (H) = (100 m/s)² / (2 * 10 m/s²) = 500 meters
• Equation for time to reach maximum height (t) = initial velocity (v) / acceleration due to gravity (g)
• Therefore, time to reach maximum height (t) = 100 m/s / 10 m/s² = 10 seconds

Gravity and Motion

• A vertically thrown stone falls back to earth due to gravity's constant pull.
• Satellites remain in orbit because they are constantly falling towards the Earth but also moving horizontally at a velocity that keeps them from hitting the ground.

Uniform Circular Motion

• The time of revolution in uniform circular motion is constant.
• The speed of the object in uniform circular motion is constant.
• The path followed by the object is circular.
• The velocity of the object continuously changes due to the changing direction, even though the speed remains constant.

Gravitational Potential Energy

• As an apple falls from a tree, its gravitational potential energy converts into kinetic energy.
• Upon reaching the ground, the apple's gravitational potential energy becomes zero.

Object Thrown Upward

• When an object is thrown upwards, its velocity decreases due to gravity's pull until it reaches its peak height.
• After reaching its peak, the object accelerates downwards due to gravity, increasing its velocity.

Rope Walker

• A rope walker needs a long pole to maintain balance.
• The pole shifts the center of gravity of the rope walker, providing stability by keeping the center of gravity over the tightrope.
• Without the pole, the rope walker's center of gravity would not be aligned with the rope, leading to loss of balance and a likely fall.

Weight in a Lift

• When a lift descends, a person's weight decreases, making them feel lighter.
• This is because the acceleration due to gravity decreases as the lift descends.

Projectile Motion: Time of Flight

• Equation for total time of flight (T) = (2 * initial velocity (v)) / acceleration due to gravity (g)
• Given initial velocity (v) = 20 m/s and acceleration due to gravity (g) = 10 m/s²
• Therefore, total time of flight (T) = (2 * 20 m/s) / 10 m/s² = 4 seconds

This quiz explores the fundamental concepts of gravity, including its effects on objects and life on Earth. It also covers the center of gravity, circular motion, and how to calculate weight using gravitational force. Test your understanding of these key physics principles.