Suppose it takes at least 5 people to push a very heavy box up a 400-cm ramp. If there are actually 6 people there to help push, which ramp(s) could they use to get the box moved? (Assume no friction)

A 200-cm ramp
B. 400-cm ramp
C. 800-cm ramp
D. Either the 400-cm ramp or the 800-cm ramp would work.

Roger pushes a box on a 30° incline. if he applies a force of 60 newtons parallel to the incline and displaces the box 10 meters along the incline, how much work will he do on the box? a. 5.2 × 102 joules b. 6.0 × 102 joules c. -5.2 × 102 joules d. -6.0 × 102 joules

While strolling downtown on a saturday afternoon, you stumble across an old car show. as you are walking along an alley toward a main street, you glimpse a particularly stylish alpha romeo pass by. tall buildings on either side of the alley obscure your view, so you see the car only as it passes between the buildings. thinking back to your physics class, you realize that you can calculate the car's acceleration. you estimate the width of the alleyway between the two buildings to be 6 m. the car was in view for 0.6 s. you also heard the engine rev when the car started from a red light, so you know the alpha romeo started from rest 4 s before you first saw it. find the magnitude of its acceleration.

What is reflection, what is refraction, and what is diffraction. what some similarities or differences between the three.