Question

what do you mean by work ? give an example of negative work done . what is the work to done to increase the velocity of the car from the 18 km/hour to 90 km/hour if the mass of car is 2000 kg ?​

Answer 1

When we lose energy we do work.

20+555554*5=65665655

Answer 2

AnswEr:

$\huge \sf \: Work \: \colon -$

Work is said to be done when an applied force produces a displacement in the body in the given direction.

Example of negative work :

• When we kick a football lying on the ground, the force of our kick moves the football. When the football dhows due to force of friction acting in a direction opposite to the direction of motion of football, thus work done is negative.

• Work done by force of friction is negative because this force is acting opposite to the direction of displacement.

_________________________

Given,

• Initial velocity = 18 km / h

$\therefore \tt \: = 90 \times \frac{5}{18} = 25 \: m/s$

• Final Velocity = 90km/ h

$\therefore \tt \: 18 \times \frac{5}{18} = 5 \: m/s$

• m = 2000 kg

Work done = change in kinetic energy

$\longrightarrow \sf \frac{1}{2} \:m( {v}^{2} - {u}^{2} ) \\ \\ \longrightarrow \sf \frac{1}{2} \times 2000 \: ( {25}^{2} - {5}^{2} ) \\ \\ \longrightarrow \sf 1000 \: (625 - 25) \\ \\ \longrightarrow \sf \: 1000 \times 600 \\ \\ \longrightarrow \sf \: 600000 \: J \\ \\ = \sf \: 600 \: K.J$