When an automobile moves with constant velocity, the power developed is used to overcome the frictional forces exerted by the air and the road. If the engine develops 40 hp, what total frictional force acts on the car at 140 mph

476.82 N

Explanation:

In the given question, the speed of the car is given in mph,

therefore to convert mph in meter per second

= ( 140 x 1609) / 3600

= 62.58

Now, to find the frictional force, convert the power of the car that is hp into watt

we know, 1 hp = 746 W

therefore, 40 x 746

= 29840 watts.

Frictional force,

= power/ speed of car

= 29840/ 62.58

= 476.82 N

Thus, 476.82 N is the correct answer.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)

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