Teaching Physics with the Physics Suite Edward F. Redish Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP

Fan carts P&E

 Two fan carts labeled A and B are placed on opposite sides of a table with their fans pointed in the same direction as shown in the figure below. Cart A is weighted with iron bars so it is twice as heavy as cart B. When the fans are turned on, they cause the air to exert a constant force of the cart independent of its mass. Assume that friction is small enough to be neglected. The fans are set with a timer so that after they are switched on, they stay on for a fixed length of time, Δt, and then are turned off.
(a) Just after the fans are turned off, which of the following statements are true about the momenta of the two carts?

(i) pA > pB
(ii) pA = pB
(iii) pA < pB

(b) Just after the fans are turned off, which of the following statements are true about the kinetic energies of the two carts?

(i) KA > KB
(ii) KA = KB
(iii) KA < KB

(c) Which of the following statements are true? You may choose as many as you like, or none. If you choose none, write N.

(i) After the fan is turned on, each cart moves at a constant velocity, but the two velocities are different from each other.
(ii) The kinetic energy of each cart is conserved.
(iii) The momentum of each cart is conserved.