At an instant when a particle of mass 80 g has a velocity of 25 m/s in the positive y direction, a 75-g particle has a velocity of 20 m/s in the positive x direction. What is the speed of the center of mass of this two-particle system at this instant? a. 16 m/s
b. 45 m/s
c. 23 m/s
d. 20 m/s
e. 36 m/s

Now that the first three steps have been explained, identify the next three steps, in order. calculate the magnitude of r sum vector components calculate a and b magnitudes calculate the direction of r, calculate x,y components step 4 step 5 step 6

Which are examples of projectile motion? choose all that apply a. a soccer ball rolling across the ground in the northeast direction b. a car turning a corner, so it is heading south c. a javelin flying through the air d. a tennis ball lobbed over the net

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.