AP physics questions

Hi guys, i'm preparing for the AP physics exam.... please help me answer these questions. thank you.

9. A diver initially moving horizontally with speed v dives off the edge of a vertical cliff and lands in the water a distance d from the base of the cliff. How far from the base of the cliff would the diver have landed if the diver initially had been moving horizontally with speed 2v ?

(A) d
(B) root(2d)
(C) 2d
(D) 4d
(E) It cannot be determined unless the height of the cliff is known.

10. Two bodies of masses 5 and 7 kilograms are initially at rest on a horizontal frictionless surface. A light spring is compressed between the bodies, which are held together by a thin thread. After the spring is released by burning through the thread, the 5?kilogram body has a speed of 1/5 meter per second. The speed of the 7?kilogram body is

(A) 1/12 m/s
(B) 1/7 m/s
(C) 1 / root(35)   m/s
(D) 1/5 m/s
(E) 7/25 m/s

5. A 2?kilogram block rests at the edge of a platform that is 10 meters above level ground. The block is launched horizontally from the edge of the platform with an initial speed of 3 meters per second. Air resistance is negligible. The time it will take for the block to reach the ground is most nearly

(A) 0.3 s
(B) 1.0 s
(C) 1.4 s
(D) 2.0 s
(E) 3.0 s

6 A horizontal force F is used to pull a 5?kilogran block across a floor at a constant speed of 3 meters per second. The frictional force between the block and the floor is 10 newtons. The work done by the force F in 1 minute is most nearly

(A) 0 J
(B) 30 J
(C) 600 J
(D) 1,350 J
(E) 1,800 J


21. A square loop of copper wire is initially placed perpendicular to the lines of a constant magnetic field of 5 x 10-3 tesla. The area enclosed by the loop is 0.2 square meter. The loop is then turned through an angle of 90° so that the plane of the loop is parallel to the field lines. The turn takes 0.1 second. The average emf induced in the loop during the turn is

(A) 1.0 x 10-4 V
(B) 2.5 x 10-3 V
(C) 0.01 V
(D) 100 V
(E) 400 V

22. James Joule did much to establish the value of the

(A) universal gravitational constant
(B) speed of light
(C) mechanical equivalent of heat
(D) charge of an electron
(E) specific heat capacity of helium

23. An ideal gas in a closed container initially has volume V, pressure P. and Kelvin temperature T. If the temperature is changed to 3T. which of the following pairs of pressure and volume values is possible?

(A) 3P and V
(B) P and V
(C) P and V/3
(D) P/3 and V
(E) 3P and 3V

my answers are B B C A C D B
i really have no idea how to do some of them...
Thanks for helping.