A person is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: force the person exerts on the crate, normal force exerted on the crate by the floor, and weight force exerted on the crate by the earth. Required:
How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

The free body diagram shows a box being pulled to the left up a 25-degree incline. the magnitude of the normal force is

The speed of light can be used to measure the

At a certain instant after jumping from the airplane a, a skydiver b is in the position shown and has reached a terminal (constant) speed vb = 52 m/s. the airplane has the same constant speed va = 52 m/s, and after a period of level flight is just beginning to follow the circular path shown of radius ρa = 2330 m. (a) determine the velocity and acceleration of the airplane relative to the skydiver. (b) determine the time rate of change of the speed vr of the airplane and the radius of curvature ρr of its path, both as observed by the nonrotating skydiver.