Work and powerIB MYP Physics: Flashcards

What these 13 flashcards ask

State the equation for work done.
What is 1 joule in terms of newtons and metres?
How is work done related to energy transferred?
State the equation for power.
What is 1 watt?
A 30 N force moves a box 4.0 m. How much work is done?
A machine does 900 J of work in 30 s. What is its power?
How many watts are in 1 kW?
How many watts are in 1 MW?
Convert 2.5 kW into watts.
A 3.0 kW heater runs for 10 s. How much energy does it transfer?
Why does pushing a crate at steady speed still need work to be done?
Which time unit must you use in P = W ÷ t?

Exam questions on Work and power

A removal worker in Lagos pushes a crate across a warehouse floor with a constant horizontal force of 150 N. The crate moves 8.0 m in 20 s at a steady speed.
The crate moves at a steady speed, so its kinetic energy does not change. Explain where the energy transferred by the worker goes.2 marks
A motor in a lift at an office tower in Singapore raises the lift car and its passengers, which have a total weight of 8000 N, through a height of 30 m in 40 s.
Explain why the new motor has a greater power than the original motor even though it does not do more work.2 marks
A student investigates whether carrying a bag changes the power she develops when she runs up a staircase. The staircase rises 4.0 m vertically and the student has a weight of 500 N. Without a bag, she completes the climb in 5.2 s, 4.8 s and 5.0 s on three trials, timed with a stopwatch.
Identify the independent variable, the dependent variable and one control variable in an investigation into the effect of carrying a bag on her power.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).