A 4.0 kg mass is 1.0 m away from a 7.0 kg mass. What is the gravitational force between the two masses? (Remember to use the gravitational constant, G = 6.67 x 10-11 N x m2/ kg2, in your calculation.) 6.67 x 1010N
1.9 x 10-9N
3.8 N
6.67 x 10-11 N

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?