Sci

• When you throw something up, acceleration is 9.8 m/s downward which is constant
• The velocity of an object in free fall changes by 9.8 m/s every second of fall
• A car has uniform or constant acceleration if it maintains a constant change in its velocity in each time interval along a straight line
• Velocity in projectile motion


  Constant at the x-axis
• Acceleration in projectile motion

  Constant at the y-axis
• Projectile motion is made of two motions that are independent of each other
• The acceleration on the x-axis is 0 while on the y-axis is 9.8
• Solving for final velocity and height of a ball dropped from a hill

  1. Ball falls for 2.6 seconds

  2. Find final velocity

  3. Find height of hill
• The horizontal component equations to be used when a projectile is launched horizontally are: v_x = u_x + at and x = u_x*t + 1/2*a*t^2
• The vertical component equations to be used when a projectile is launched horizontally are: v_y = u_y + at and y = u_y*t + 1/2*a*t^2
• Solving for the horizontal distance a stone strikes the ground when thrown horizontally from a cliff

  1. Initial horizontal velocity of 8 m/s

  2. Cliff height of 80 m

  3. Compute horizontal distance
• The ball strikes the ground 32.32 m from the base of the cliff after 4.04 s
• Range (R)


  The horizontal distance of a projectile
• Height


  The vertical distance of a projectile
• The maximum range of a projectile can be attained if it is launched at an angle of 45°
• To achieve the farthest range, the projectile should be launched at an angle of 45° (neglecting air resistance)
• The horizontal range is minimum when the angle of the projectile (θ) is 90°
• In projectile motion, the vertical component or height is affected by the force of gravity
• Solving for the angle to achieve the same range as a 70° launch

  1. Given: 70° launch, 50 m range

  2. Find: Complementary angle (20°) with same initial velocity and range
• Solving for the velocity at the highest point of a projectile launched at 37° with 250 m/s


  1. Initial velocity of 250 m/s at 37°

  2. Find velocity at highest point
• If a bus has twice the mass but the same speed, its momentum is doubled
• Momentum is conserved when there is no external force, the total momentum of the system remains the same before and after the collision
• Impulse


  The impact that a force has on an object over a period, change in momentum
• A ball that rebounds at the same speed as it hit the ground undergoes an elastic collision
• As a pendulum swings from lowest to highest position

  Kinetic energy decreases, potential energy increases
• The total mechanical energy remains the same if the kinetic energy of an object increases
• Conservation of mechanical energy is observed when a resting football is kicked and set in motion
• At the highest point of a pendulum's swing (point B)


  Potential energy is maximum, kinetic energy is minimum
• As the potential energy of a falling object decreases, its total mechanical energy remains the same
• Calculating the potential energy of a 5 kg object dropped from 10 m

  PE = m*g*h = (5 kg)*(9.8 m/s^2)*(10 m) = 490 J
• A stretched rubber band that is loosened does not describe potential energy converted into kinetic energy
• A can of soft drinks remains at a constant cool temperature in a refrigerator because the amount of heat flowing in equals the heat flowing out
• Calculating the change in internal energy of 200 g of water with 400 J of work done and 200 calories of heat added

  Change in internal energy = 400 J + (200 cal * 4.184 J/cal) = 1237.36 J