# Force, motion and energy problems and answers

Recent questions in Force, Motion and Energy
Armorikam 2020-10-23

### A lunch tray is being held in one hand, as the drawing illustrates. The mass of the tray itself is 0.200 kg, and its center of gravity is located tits geometrical center. On the tray is a 1.00 kg plate of food and a 0.190 kg cup of coffee. Obtain the force T exerted by the thumb and the force F exerted by the four fingers. Both forces act perpendicular to the tray, which is being held parallel to the ground.

midtlinjeg 2020-10-21

### An 80.0-kg skydiver jumps out of a balloon at an altitude of1000 m and opens the parachute at an altitude of 200 m. (a) Assuming that the total retarding force on the diver is constant at 50.0 N with the parachute closed and constant at 3600 N with the parachute open, what is the speed of the diver whenhe lands on the ground? (b) Do you think the skydiver will be injured? Explain. (c) At what height should the parachute be opened so that the final speed of the skydiver when he hits the ground is 5.00m/s? (d) How realistic is the assumption that the total retarding force is constant? Explain.

melodykap 2020-10-18

### A weatherman carried an aneroid barometer from the groundfloor to his office atop a tower. On the ground level, the barometer read 30.150 in Hg absolute; topside it read 28.607 in hg absolute. Assume that the average atmospheric air density was 0.075lb/ft3, estimate the height of the building.

beljuA 2020-10-18