Home
Class 12
PHYSICS
When a man walks on a horizontal surface...

When a man walks on a horizontal surface with constant velocity work done by the

A

Friction is zero

B

Contact force is zero

C

Gravity is zero

D

Man is zero

Text Solution

Verified by Experts

The correct Answer is:
D
Since mg & N are perpendicular to velocity `vec(v)` and `dvec(s)`, work done by these forces is zero. Since no relative sliding occurs during walking, static friction comes into play. Hence the point of application of static frictional force does not move. Therefore no work is done by frictional force.
The man has to lose his body.s (internal ) energy E, hence performs work because `W=DeltaE`.
Hence (D) is correct.
Promotional Banner

Similar Questions

Explore conceptually related problems

A disc of radius R is rolling purely on a flat horizontal surface, with a constant angular velocity the angle between the velocity ad acceleration vectors of point P is

A disc of radius R is rolling purely on a flat horizontal surface, with a constant angular velocity. The angle between the velocity ad acceleration vectors of point P is

A disc of radius R is rolling purely on a flat horizontal surface, with a constant angular velocity. The angle between the velocity and acceleration vectors of point P is .

The sign of work done by a force is important to understant. State carefully if the following quantities are positive or negative. (a) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket. (b) Work done by the gravitational force in the above case. (c ) Work done by friction on a body sliding down an inclined plane. (d) Work done by an applied froce on a body moving on a rough horizontal plane with uniform velocity. (e ) Work done by the resistive force of air on a vibrating pendulum in bringing it to rest.

A man of mass m starts moving on a plank of mass M with constant velocity v with respect to plank. If the plank lies on a smooth horizontal surface, then velocity of plank with respect to ground is

One end of a light spring of spring constant k is fixed to a wall and the other end is tied to a block placed on a smooth horizontal surface. In a displacment, the work done by the spring is +(1/2)kx^(2) . The possible cases are.

One end of a light spring of spring constant k is fixed to a wall and the other end is tied to a block placed on a smooth horizontal surface. In a displacement, the work done by the spring is +(1/2)kx^(2) . The possible cases are.

A particle of mass m is projected at an angle alpha to the horizontal with an initial velocity u . The work done by gravity during the time it reaches its highest point is

A block of mass m is pulled slowly by a minimum constant force on a rough ( mu ) horizontal surface through a distance x. Find work done by force F.

A block of mass m is kept over another block of mass M and the system rests on a horizontal surface. A constant horizontal force F acting on the lower block produces an acceleration (F)/(2(m+M)) in the sytem. The two blocks always move together. Consider displacement d of the system. a. Find the work done by friction on bigger block. b. Find the coefficient of kinetic friction between the bigger block and the horizontal surface. c. Find the frictional acting on the smaller block. d. Find the work done by the force of friction on the smaller block by the bigger block. e. Find the work done by static friction on bigger block.