PLEASE HELP !!

On Earth we can easily see Mercury, Venus, and Mars in the night sky. The planets look like they are moving through the stars because the

A) Earth is orbiting the Sun.
B) sky is swirling overhead on Earth.
C) all objects in space orbit around the Earth.
D) planets are moving in their own orbit around the Sun.

The rigid beam is supported by the three suspender bars. bars ab and ef are made of aluminum and bar cd is made of steel. if each bar has a cross-sectional area of 450 mm2, determine the maximum value of p if the allowable stress is (σallow)st = 200 mpa for the steel and ( σallow)al = 150 mpa for the aluminum. est = 200 gpa and eal = 70 gpa.

The dot diagram represents the motion of the motorcycle as it moves from left to right

A0.580-kg rock is tied to the end of a string and is swung in a circle with a radius of 0.500 meters. the velocity of the rock is 4.50 m/s. what is the centripetal force acting on the rock? 15.5 n 5.22 n 69.8 n 23.5 n