Practice Problems
15 curated problems with step-by-step solutions
Topic
Difficulty
Efficiency
3 problems
Lifting a Crate with a Pulley
A worker uses a simple pulley to lift a 200 N crate. They apply 250 J of work input and the crate rises by 1 m.
Given
What is the efficiency of the pulley system?
Electric Motor Efficiency
An electric motor receives 500 J of electrical energy and produces 375 J of mechanical work.
Given
Calculate the efficiency of the motor and the energy wasted.
Car Engine Performance
A car engine burns fuel releasing 8,000 J of chemical energy. The engine moves the car with 5,600 J of kinetic energy. The rest is lost as heat.
Given
Find the efficiency and the energy wasted as heat.
Mechanical Advantage
3 problems
Simple Crowbar
A mechanic uses a crowbar to lift a 600 N engine block. They apply only 150 N of effort.
Given
What is the mechanical advantage of the crowbar?
Hydraulic Jack
A hydraulic jack lifts a 3,600 N car. The operator pushes with 90 N of effort.
Given
Calculate the mechanical advantage. Is this a force multiplier?
Tweezers (Speed Multiplier)
Tweezers require 8 N of effort to grip an object with 4 N of gripping force. The effort arm is shorter than the load arm.
Given
Find the MA and explain what type of machine this is.
Pulleys
3 problems
Single Fixed Pulley
A student uses a single fixed pulley to lift a 300 N bucket of sand. The rope is pulled 2 m.
Given
What effort is needed and what is the mechanical advantage?
Block and Tackle (4 Pulleys)
A block-and-tackle system with 4 pulleys is used to lift a 800 N load. The rope is pulled 4 m.
Given
Find the effort force, MA, and load rise distance.
Crane Pulley System
A construction crane uses 6 pulleys to lift a 2,400 N steel beam. The rope is pulled 12 m. Assume 80% efficiency.
Given
Find the actual effort needed accounting for efficiency.
Inclined Planes
3 problems
Loading Dock Ramp
A loading ramp is 5 m long and 1 m high. A 500 N box needs to be pushed up the ramp.
Given
What effort is needed to push the box up the ramp?
Wheelchair Ramp
A wheelchair ramp is 6 m long and rises 0.75 m. A person in a wheelchair weighs 900 N total.
Given
Calculate the effort needed and the ramp angle.
Ski Slope Work Calculation
A skier of mass 70 kg (weight ≈ 686 N) is pulled up a ski slope 200 m long with a vertical rise of 40 m.
Given
Find the effort force, MA, angle, and work done along the slope.
Levers
3 problems
Seesaw (Class 1 Lever)
Two children sit on a seesaw. Child A (load = 400 N) sits 1.5 m from the pivot. Child B sits 2 m from the pivot.
Given
What effort (weight) does Child B need to balance the seesaw?
Wheelbarrow (Class 2 Lever)
A wheelbarrow carries a 600 N load of soil. The load is 0.5 m from the wheel (fulcrum). The handles are 1.5 m from the wheel.
Given
How much effort is needed to lift the wheelbarrow handles?
Fishing Rod (Class 3 Lever)
A fishing rod is a Class 3 lever. The hand grips 0.3 m from the fulcrum (elbow). The fish (load) is 1.8 m from the fulcrum.
Given
Find the effort needed and explain why MA < 1 is useful here.