Question

You are working out on a rowing machine. Each time you pull the rowing bar (which simulates the oars) toward you, it moves a distance of 1.2 m in a time of 1.7 s. The readout on the display indicates that the average power you are producing is 89 W. What is the magnitude of the force that you exert on the handle?

Answer 1

Answer:

The force exerted on the handle of the rowing machine is : Force = 126.08 Newtons

Explanation:

since power is described as rate of doing work,

$power = \frac{work}{time}$

therefore,

work = power x time = 89 x 1.7 = 151.3 Joule

Hence, the total work done is 151.3 Joule

Now, using the formula for work done to calculate the final force

Work = Force x Distance

$Force = \frac{work}{distance}$

$Force = \frac{151.3}{1.2}$

Force = 126.08 Newtons is the force exerted on the handle.

Answer 2

Answer:

F = 125N.

Explanation:

The power generated by you is given by

P = F•v

v is the instantaneous velocity of the machine moving towards you.

F is the force you apply which is parallel (should be parallel for maximum power) to the direction of velocity.

The power is a scalar quantity resulting from the vector product of two vectors but in this problem the technique of working with scalar product of vectors is not required.

So the velocity v = distance/time taken = 1.2/1.7 =

0.71m/s

Since P = Fv, then F = P/v

Given that P = 89W

F = 89/0.71 = 125N.