Three particles lie in the xy plane. particle 1 has mass m1 = 6.7 kg and lies on the x-axis at x1 = 4.2 m, y1 = 0. particle 2 has mass m2 = 5.1 kg and lies on the y-axis at x2 = 0, y2 = 2.8 m. particle 3 has mass m3 = 3.7 kg and lies at the origin. what is the direction of the net gravitational force on particle 3, expressed as an angle counterclockwise from the +x-axis?

The force needed to overcome static friction is usually less than that needed to overcome kinetic friction.true or false?

An object in mechanical equilibrium is an object

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?