Fred is playing the slot machines. after a certain number of plays, he wins a few coins, but fred is unable to determine how many plays he needs to win. which of the following statements is true? a. fred is on a fixed-interval schedule of reinforcement. b. fred is on a variable-interval schedule of reinforcement. c. fred is on a fixed-ratio schedule of reinforcement. d. fred is on a variable-ratio schedule of reinforcement.

When considering gravity acceleration and the force of acceleration, what must be true? a. the direction of acceleration must be perpendicular to the direction of the force. b. the direction of the force and the direction of acceleration must be the same as each other. c. the direction of the force and the direction of acceleration must be opposite of each other. d. the mass of the body must be the same as the acceleration of the body.

Aclarinetist, setting out for a performance, grabs his 3.350 kg clarinet case (including the clarinet) from the top of the piano and carries it through the air with an upward force of 24.65 n. find the case's vertical acceleration. indicate an upward acceleration as positive and a downward one as negative.

Explain why electric current cannot exist if a current doesn't have a voltage source.