g8 science

• Experiences of riding a car

  • Car exhilarates abruptly, making you feel as if your body is pulled to the back
  • Driver suddenly steps on the brakes, and you feel the seat belt tighten
• Newton's first law of motion

  The law of inertia, which explains how an object responds to changes in motion
• Force


  Any push or pull that causes changes in the motion of an object
• Types of force


  • Contact force
  • Non-contact force
• Contact force


  Present when two or more surfaces or media touch and interact
• Friction


  A specific type of contact force, the object's resistance to motion
• Non-contact force


  Constantly present in nature and does not need human intervention to arise
• Non-contact force


  • The sun and planets exerting a gravitational pull on each other despite their large spatial separation
• Aspects of motion


  • Speed
  • Velocity
  • Acceleration
• Speed


  The length of distance traveled in a certain amount of time
• Velocity


  The rate of change of displacement of an object
• Acceleration


  The rate of change of velocity of an object
• Motion examples


  • Car going 100 miles per hour (speed)
  • Car going 100 miles per hour east (velocity)
  • Car slowing down at the stop sign, then speeding up (acceleration)
• Newton's first law of motion


  The response of an object to changes in motion
• Parts of Newton's first law of motion

  • An object at rest will remain at rest unless acted on by an unbalanced force
  • An object in motion continues to move with the same velocity unless acted on by an imbalanced force
• Inertia


  The property that resists the changes in an object, independent from external force and mass-dependent
• Inertia examples


  • Box at rest, acted upon by normal force and gravitational force (balanced forces)
  • Spacecraft in space, with engines turned off (constant speed and direction)
  • Riding a car, experiencing sudden stop (inertia keeps you moving)
• Activity with coin, glass, and cardboard

  1. Arrange setup, slowly pull cardboard

  2. Arrange setup, quickly flick cardboard
• An object at rest will remain at rest, and an object in motion will remain in motion, unless acted on by an unbalanced force
• What are the two types of energy discussed in the video?

  Kinetic energy and potential energy
• What does the term "kinetic" refer to in kinetic energy?

  Kinetic refers to motion
• What does kinetic energy represent?


  Kinetic energy represents energy in motion
• What is the formula for kinetic energy?


  $KE =$$\frac{1}{2} m v^2$
• What factors does kinetic energy depend on?

  Kinetic energy depends on mass and speed of the object
• What are the units for mass and speed in the kinetic energy formula?

  Mass is in kilograms and speed is in meters per second
• If you double the mass of an object, what happens to its kinetic energy?

  The kinetic energy will double
• If you double the speed of an object, what happens to its kinetic energy?

  The kinetic energy will quadruple
• How can you determine the change in kinetic energy if you increase the mass by a factor of three and quadruple the speed?

  The kinetic energy will increase by a factor of 48
• What is potential energy?

  Potential energy is a form of stored energy due to position
• How does the height of an object affect its gravitational potential energy?

  An object at a higher position has more gravitational potential energy
• What is the formula for gravitational potential energy?


  $PE =$$mgh$
• What does each variable in the gravitational potential energy formula represent?

  m is mass in kilograms, g is gravitational acceleration in meters per second squared, and h is height in meters
• What is the value of gravitational acceleration on Earth?

  1. 8 meters per second squared
• How do you calculate the gravitational potential energy of a 10 kg ball at a height of 50 meters?

  The gravitational potential energy is 4900 joules
• What happens to potential energy as an object falls?

  The potential energy decreases while kinetic energy increases
• At position B, just above the ground, what is the potential energy of the ball?

  The potential energy is zero
• What is the relationship between potential energy at position A and kinetic energy at position B?

  The potential energy at position A is equal to the kinetic energy at position B
• How can you find the speed of the ball just before it touches the ground using kinetic energy?


  By using the formula $KE =$$\frac{1}{2} m v^2$ and solving for v
• What is the speed of the ball just before it hits the ground if its kinetic energy is 4900 joules and mass is 10 kg?

  The speed is approximately 31.3 meters per second
• What is elastic potential energy?

  Elastic potential energy is stored energy in a compressed or stretched spring