Boy, was that a lot of work

Classical Mechanics Level 3

How much work, in Joules, should a boy of 50 kg do in order to change his velocity from $36\text{ km/hr}$ to $54 \text{ km/hr}$ ?

Assumptions and Details

2 solutions

A Former Brilliant Member
Feb 22, 2017

why is it level 4?

Exactly! BTW, are you in Slack?

Swapnil Das - 4 years, 3 months ago

No,are you there?

A Former Brilliant Member - 4 years, 3 months ago

I'm there in my channel with 25 others. Want to join?

Swapnil Das - 4 years, 3 months ago

@Swapnil Das – yeah sure!!!

A Former Brilliant Member - 4 years, 3 months ago

@A Former Brilliant Member – Give me your email here. I'll send you an invite?

Swapnil Das - 4 years, 3 months ago

This is Overrated man!

Md Zuhair - 4 years, 3 months ago

Lol, This is a 9th class NCERT level question.

Swapnil Das - 4 years, 3 months ago

Ya you are absolutely correct

Md Zuhair - 4 years, 3 months ago

Aditya Chauhan
Dec 12, 2015

Since we have to give the answer in joules , we should first convert the velocity into SI Unit. 36km/h = 10m/s

54km/h = 15m/s

Using Work Energy Theorem

Work Done = Change in Kinetic Energy

= $\dfrac{1}{2} \times m \times \Delta v^{2}$

= $\dfrac{1}{2} \times 50 \times (15^{2}-10^{2})$

= $25 \times 125$

= $\boxed{3125 J}$