A car has 400 kgm/s worth of momentum and runs into a truck initially at rest. After the collision, the truck has 500 kgm/s worth of momentum. What must be the final momentum of the car and truck combined? A. 500 kgm/s
B. 100 kgm/s
C. 400 kgm/s
D. -100 kgm/s

Which of the following represents a virtual image?

If an inclined plane is 5 m long and 2 m high, what is its mechanical advantage? a. 2.5 b. 3 c. 7 d. 10

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.