A battery-powered project cart of mass 8kg moves along a straight, horizontal track. Three horizontal forces act on the cart in the same line:
• the motor provides a forward thrust of 60N,
• air resistance exerts 12N backward,
• rolling friction at the wheels provides 20N backward.
(i) While the motor is on, calculate the net force on the cart and state whether the forces are balanced or unbalanced.
(ii) Determine the acceleration of the cart in this interval.
(iii) Assuming the cart starts from rest, calculate the distance it travels in the first 5s.
(iv) After 5s the motor is switched off. Only air resistance and rolling friction now act on the cart. Compute the new net force and comment on whether the forces are balanced or unbalanced.
(v) Explain qualitatively how the motion of the cart will change during the next few seconds after the motor is turned off.