A1.2-kg object moving with a speed of 8.0 m/s collidesperpendicularly with a wall and emerges with a speed of 6.0 m/s inthe opposite direction. if the object is in contact with the wallfor 2.0 ms, what is the magnitude of the average force on theobject by the wall?
a. 9.8 knb. 8.4 knc. 7.7 knd. 9.1 kne. 1.2 kn

The base of a 50-meter tower is at the origin; the base of a 50-meter tree is at (0, 50, 0). the ground is flat and the z-axis points upward. the following parametric equations describe the motion of six projectiles each launched at time t = 0 in seconds. (i) r (t) = (50 + t2)k (ii) r (t) = 2t2 j + 2t2k (iii) r (t) = 50 i + 50 j + (50 − t2)k (iv) r (t) = 2t j + (50 − t2)k (v) r (t) = (50 − 2t) i + 2t j + (50 − t)k (vi) r (t) = t i + t j + tk (a) which projectile is launched from the top of the tower and goes downward? at time t = , the projectile hits the ground at point (x, y, z) = . (b) which projectile hits the top of the tree?