Focus on the following concepts: Mechanical Energy, Potential Energy (PE), Kinetic Energy (KE), Work, Power, Momentum, and Hooke’s Law.
Utilize notes and worksheets for studying.
Access resources on Google Classroom for key answers and review material.
Understand how to rearrange formulas since original formulas will be on the test.
Familiarize yourself with units and abbreviations that correspond to specific terms and formulas.
Definition of Work: Work is done when a force causes displacement.
Example of Work Being Done: Pushing a box across the floor (force applied and movement occurs).
Example of No Work: Carrying a bag of groceries while walking horizontally (no displacement in the direction of the force).
Explanation: Work is considered to be done only when the force applied results in an object being moved.
Power (P): The rate at which work is done (measured in watts).
Example Calculation of Work: If Jan generates 450 watts in 6 seconds, then
Work (W) = Power (P) x Time (t) => W = 450 W x 6 s = 2700 J.
Minimum Power: A machine adds 5,000 J in 20 seconds. To find power, use
Power = Work / Time => P = 5000 J / 20 s = 250 W.
Formula: KE = 1/2 mv^2.
Calculate KE for a volleyball with mass 2.0 kg and velocity 30 m/s:
KE = 1/2 x 2.0 kg x (30 m/s)^2 = 900 J.
Formula: PE = mgh, where m is mass, g is gravitational acceleration (9.81 m/s²), and h is height.
An apple hanging 5.0 m with mass 0.2 kg:
PE = 0.2 kg x 9.81 m/s² x 5.0 m = 9.81 J.
A crane holding a concrete block weighing 2200 N at 10 m:
PE = Weight x Height = 2200 N x 10 m = 22000 J.
For a mass of 15 kg and PE of 200 J:
Use PE formula to find height: 200 J = 15 kg x 9.81 m/s² x h
Calculate height h = 200 J / (15 kg x 9.81 m/s²) = 1.36 m.
To find velocity of the previous mass when at PE of 200 J, use:
KE = PE (if no energy lost) => KE = 200 J, then find v using KE formula:
200 J = 1/2 x 15 kg x v^2 => v = sqrt(200 J / (1/2 x 15 kg)) = 4.90 m/s.
Spring Force: F = kx, where k is the spring constant and x is the extension.
For a spring constant of 10 N/m and extension of 0.3 m:
F = 10 N/m x 0.3 m = 3 N.
To find spring constant with a 6 N weight extended by 0.2 m:
k = F/x = 6 N / 0.2 m = 30 N/m.
Momentum (p): p = mv, where m is mass and v is velocity.
Calculate momentum for 125.0 kg ball at 6.5 m/s:
p = 125.0 kg x 6.5 m/s = 812.5 kg·m/s.
For the falling rock with momentum 200 kg·m/s and velocity 5.0 m/s:
mass m = p/v = 200 kg·m/s / 5.0 m/s = 40 kg.
Find velocity for an 8.5 kg ball with momentum of 293 kg·m/s:
v = p/m = 293 kg·m/s / 8.5 kg = 34.47 m/s.
Potential Energy (PE) is always highest at the top of a hill or structure.
Kinetic Energy (KE) is always highest when the object is in motion.
Where PE is Lowest? When the object is at the bottom or ground level.
Where KE is Lowest? When the object is at rest.