Question

What what do you mean by work give an example of negative work then what is the work done increasing the velocity of a car from 18 km per hour 19 km per hour if the mass of the car is 2000 kg

Answer 1

In simple term work is a physical quantity(having only magnitude but no direction) in which certain conditions are needed tobe satisfied for it to be done.
OR
Work is said to be done if and only if a force is acting on the body produces motion In it in the direction of the force applied.
work done is given by,
W = Fscosx where x is the angle between the force and the direction of the motion of the object

example of negative work done :
1) when a stone is thrown upwards its motion is opposed by the gravity of the earth, the angle between the force of gravity and the stone is 180 degree, then
Work done W = Fscos180
W=-Fs [ cos 180 =-1]

solution for the numerical problem :
given,
Initial velocity of the car u=18km/h=18x1000/60x60=5m/s
final velocity V =19km/h=19x1000/60x60=5.28m/s
mass m =2000kg
using Newton law of motion, V^2-u^2=2as
2aS =(5.28)^2-(5)^2
2aS =27.8784-25
aS =2.8784/2
aS =1.4392
then,
W = Fscos0 [angle is 0 degree ]
W=ma x S. [ F= ma]
W =m x (aS)
W =2000 x 1.4392
W =2878.4 joules
I HOPE THIS WILL HELP YOU.

Answer 2

when we apply force on an object and the object moves in the direction of force then it is called work

Eg of negative work when we kick a ball we applied force in forward direction but frictional force acts opposite to the force

U = 18 =18×5/18=5m/a

V=19 kmph=19×5/18=5.27m/s

W.D=f×d

W.D=m×a×d

W.D=2000× 5.27-5/2×5

Now u can do forward

Hope it helps u