At the train station, you notice a large horizontal spring at the end of the track where the train comes in. this is a safety device to stop the train so that it will not plow through the station if the engineer misjudges the stopping distance. while waiting, you wonder what would be the fastest train that the spring could stop at its full compression which is l=3 ft . to keep the passengers safe when the train stops, you assume a maximum stopping acceleration of g/2. you also guess that a train weighs half a million lbs. for purpose of getting an estimate, you decide to assume that all frictional force are negligible.

Diamond will scratch quartz. true or false

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.

Ablock having mass m slides down an inclined plane. the force of friction between the block and the inclined plane is f, the block's weight is m g, and the normal force is n. (a) draw a free – body force diagram showing the forces acting on the block. (b) write down all relevant newton’s equations for a given situation.