MA & ME Practice Problems
OBJECTIVE
 I can explain the connection between work and energy.
 I can use formulas correctly to solve for work, power, mechanical advantage, and mechanical efficiency.
 I can perform basic and multi-step algebraic functions.
Mechanical Advantage = Output Force
Input Force
Mechanical Efficiency = Work Output X 100
Work Input
Directions: Solve the following problems. Show all of your work and include the correct units.
1. You apply 200 N to a machine, and the machine applies 2,000 N to an object. What is the
mechanical advantage?
2. What is the mechanical advantage of a wheel and axle that uses 50 Newtons of force to move
a resistance of 2550 Newtons?
a. What machine is being used to make the work easier?
3. Suppose you exert 15 N on a machine, and the machine exerts 300 N on another object.
What is the machines mechanical advantage?
4. Which of the following makes work easier? A machine with a mechanical advantage of 15 or
a machine to which you apply 15 N and that exerts 255 N? Why?
5. Which of the machines has a greater mechanical advantage? A machine to which you apply
a force of 50N and the machine applies a force of 150N? Or the machine to which you apply a
force of 60N and the machine applies a force of 200N? Why?
6. Tom uses 20 Newtons of force to move a wooden box with a resistance of 130 Newtons up a
ramp. What is the mechanical advantage?
a. What machine is Tom using to make the work easier?
7. A fern receives 1055 J of light energy and through photosynthesis, converts it to 8.3 J of
energy to use for working plant system processes. What is the efficiency?
8. Your body expends 0.54 J of work to digest a steak with 2.7 J of energy. How efficient is your
body at changing that food into energy for you to use?
9. Your toaster is plugged into the counter electrical outlet. If 3.50 J of electrical energy is
supplied into the toaster to output 1.5 J of energy to toast your food, what is the efficiency of
the toaster?
10. If 360 J of energy are provided to a standard light bulb that emits 18 J of light energy, how
efficient is the light bulb?
11. Using a pulley system, a crew does 7,500 J of work to load a box that requires 4,500 J of
work. What is the efficiency of the pulley system?
BONUS
12. A particular automobile engine is rated to be 27.5% efficient in converting the energy of fuel
into useful working energy. If 1 L of gasoline contains 33.5 J of input energy, calculate the
useful energy output when 2.50 L of gasoline is consumed.