Work
The unit used to measure work.
What is a joule (J)?
The two main types of mechanical energy.
What are kinetic energy and potential energy?
The formula for efficiency.
What is efficiency = (work output ÷ work input) × 100?
The unit used to measure power.
What is a watt (W)?
The formula for mechanical advantage.
What is MA = output force ÷ input force?
The two things required for work to be done.
What are force and motion in the same direction?
The formula for kinetic energy.
What is KE = ½ m v²?
A machine is never 100% efficient because of this.
What is friction?
The formula for power.
What is power = work ÷ time?
A ramp is 6 m long and 2 m high. What is its mechanical advantage?
What is 3?
A 20 N force moves a box 3 m. How much work is done?
What is 60 J?
A 2 kg ball moves at 3 m/s. What is its kinetic energy?
What is 9 J?
A motor receives 500 J of energy but only produces 400 J of useful work. What is its efficiency?
What is 80%?
A machine does 9000 J of work in 30 s. What is its power output?
What is 300 W?
A pulley system allows a person to lift a 300 N weight using only 75 N of effort. What is its mechanical advantage?
What is 4?
If a person pushes a wall with all their strength but it doesn’t move, how much work is done?
What is 0 J?
What happens to an object’s kinetic energy if you double its velocity?
What is "it increases by four times"?
A machine requires 600 J of energy and outputs 450 J of useful work. What is its efficiency?
What is 75%?
Why is power important when comparing two machines that do the same amount of work?
What is "the one with more power does the work faster"?
A lever has an input arm of 5 m and an output arm of 2 m. What is its mechanical advantage?
What is 2.5?
Explain why carrying a backpack while walking does not count as work.
What is "the force is not applied in the same direction as motion"?
A 5 kg object is lifted 3 m. How much potential energy does it have? (Use g = 9.8 m/s²)
What is 147 J?
Why do more efficient machines save energy?
What is "they lose less energy to heat and friction"?
A runner exerts 2500 J of work in 5 seconds. How much power do they generate?
What is 500 W?
What is the trade-off when using a machine with a high mechanical advantage?
What is "you apply less force, but over a greater distance"?