A body of mass 6kg, initially moving with speed 12m/s, experiences a constant retarding force of 10 newtons for 3 seconds. Find the kinetic energy of the body at the end of this time.

F*time = change in momentum

10*3 = 6 (12-v2)
30 -72 = -6 v2
42/6 = v2 = 7m/s

KE = (1/2) 6 (49)

don't know sorry

To find the kinetic energy of the body at the end of 3 seconds, we need to use the work-energy theorem. The work done on an object by a force is equal to the change in its kinetic energy.

The work done by a force can be calculated using the formula:

Work = Force × Distance.

In this case, the distance covered by the body during the 3 seconds can be found using the formula:

Distance = Initial velocity × Time + (1/2) × Acceleration × Time^2.

Since the body is experiencing a constant retarding force, the acceleration will be in the opposite direction of motion, and its value can be calculated using Newton's second law of motion:

Acceleration = Force / Mass.

Substituting the given values, we have:

Acceleration = 10 N / 6 kg.

Now we can plug in the values to calculate the distance covered by the object during the 3 seconds:

Distance = 12 m/s × 3 s + (1/2) × (10 N / 6 kg) × (3 s)^2.

Once we have the distance, we can calculate the work done by the force:

Work = 10 N × Distance.

Finally, the change in kinetic energy of the body is equal to the work done by the force, so:

Change in Kinetic Energy = Work.

Therefore, the kinetic energy of the body at the end of 3 seconds can be calculated.