each part of the question: a. A crate is sitting in the center of a flatbed truck. The truck accelerates towards the South-East, and the crate moves with it, not sliding on the bed of the truck. What is the direction of the friction force exerted by the bed of the truck on the crate? i) To the North-West ii) To the South-East iii) To the North-East iv) There is no friction force. (Crate does not slide) b. What is true in a uniform circular motion? i) the vector velocity does not change. ii) the direction of the vector velocity is always inwards. iii) the vector acceleration does not change. iv) the direction of the vector acceleration is always inwards. c.The elastic potential energy for an ideal Spring is: I) Always negative ii) Always positive iii) Depends of the Spring is compressed or streched iv) Depends if the Spring is doing the work or the work is done on the Spring