AS/A-level Physics - Work Done

Work Done

• Work done is measured in Joules or Nm (SI unit)
• Equation for work done is:

Easy question: 📝

A box is pushed across a floor by a constant force of 100 N. What is the work done by the force to move the box 5 m?

Answer: 100 x 5 =500J

Calculating work done at an angle

• When calculating the work done by a force acting at an angle, it is useful to break the force down into components.
• Work is the energy transfer that takes place when a force causes an object to move.

• The tension in the rope can be broken down into a horizontal and a vertical component.
• The vertical component does no work because the box does not move in that direction.
• So to calculate work done by a force at an angle:

work done = force in direction of movement × distance moved

Easy question:📝

A toy car is pulled along by a piece of string which is at 30° to the horizontal. Calculate the work done in pulling the toy if the tension in the string is 10 N, and it is pulled along 5 m.

Answer:

10 x 5 x cos30°

= 43.3J

Hard question:📝

Mario is participating in the World’s Strongest Man competition. He has got one track left and it is the Truck Pull. The object is to pull the truck over a 10m distance in the shortest amount of time. Assume that the horizontal force required to pull the truck is 2200N.

1.) Does the truck move if it is pulled with a horizontal force of 2500 N at 30 degrees to the horizontal? Suggest what Mario could do to increase the horizontal force?

2.) Calculate the work done if Mario pulls the truck with the same force but at 10 degrees to the horizontal

3.) Did he pull the truck at 10 degrees? State why?

This type pf questions always appear is AS/A-level Physics exam! Practice makes perfect!👨‍🏫

Answer:

1.) Horizontal force = 2500N X cos 30 ➔ 2165 N

Therefore Mario would not be able to pull the truck at all. Go lower (suggestion) meaning reduce the angle at the horizontal

2.) Horizontal force = 2500 N X cos 10 ➔ 2462.02 N

Work Done = 2462.02 X 10m ➔ 24620.2 J or 24.6202 kJ

3.) He did because the horizontal force needed to pull the truck (2200N) was passed at 10 degrees and therefore the truck would move.

Reference:

https://getrevising.co.uk/resources/work_done_gpe_kinetic_energy

This is the end of the topic! Great job!

CLICK HERE TO LEARN MORE ABOUT OUR A-LEVEL PHYSICS COURSES

Drafted by Cherry (Chemistry)