An astronaut in an orbiting spacecraft attaches a mass m to a string and whirls it around in uniform circular motion. the radius of the circle is r, the speed of the mass is v, and the tension in the string is f. if the mass, radius, and speed were all to double the tension required to maintain uniform circular motion would be
a) f/2
b) f
c) 2f
d) 4f
e) 8f

Aperson gives a shopping cart an initial push along a horizontal floor to get it moving, and then lets go. the cart travels forward along the floor, gradually slowing as it moves. consider the horizontal force(s) on the cart while it is moving forward and slowing. which of the following statements is correct? (a) both a forward and a backward force are acting on the cart, but the forward force is larger. (b) only a forward force is acting which diminishes with time. (c) both a forward and a backward force are acting on the cart, but the backward force is larger. (d) only a backward force is acting, no forward force.