Answer:
Vf = 3.67 [m/s]
Explanation:
To solve this problem we must use the following equation of kinematics.

where:
Vf = final velocity [m/s]
Vi = initial velocity = 4.3 [m/s]
a = acceleration or desacceleration = 0.5 [m/s²]
x = distance = 5 [m]
Note: The negative sign in the above equation means that the velocity of the ball is decreasing (desacceleration).
Now replacing:
Vf² = (4.3)² - (2*0.5*5)
Vf² = 18.49 - 5
Vf² = 13.49
using the square root, we have.
Vf = 3.67 [m/s]
Answer:
F=50kg
D=5m
W=FD
therefore work done is 250Nm
Average speed = (total distance covered) / (time to cover the distance)
Total distance = (77km + 66km) = 143 kilometers
Time to cover the distance = 2 hours
Average speed = (143 km) / (2 hours) = 71.5 km per hour