(d) you observe someone pulling a block of mass 41 kg across a low-friction surface. while they pull a distance of 4 m in the direction of motion, the speed of the block changes from 5 m/s to 7 m/s. calculate the magnitude of the force exerted by the person on the block.

The magnitude of the force is 124.23 N.

Explanation:

To known the magnitude of the force is necessary to find the acceleration, that can be done by means of the equations for a a Uniformly Accelerated Motion:

 (1)

Where is the final velocity, is the initial velocity, a is the acceleration and t is the time.  

(2)

(3)

By replacing (2) in equation (3) it is gotten:

Therefore, by subtracting the first and third term ( ⇒ ) it is got:

Applying common factor for :

 (4)

Equation (4) can be rewritten in terms of t:

By knowing the time is possible to determine the acceleration by means of equation (2):

The magnitude of the force exerted by the person on the block can be determine by means of Newton's second law:

(5)

Hence, the magnitude of the force is 124.23 N.

b would be the answer