A 55-kg hiker starts at an elevation of 1600 m and climbs to the top of a 3300-m peak. (a) What is the hiker’s change in potential energy? (b) What is the minimum work required of the hiker? (c) Can the actual work done be more than this? Explain why.

Solution Step 1 of 4 Gravitational force is the attraction force exerted by the two objects on each other with certain masses. Which is directly proportional to the product of the masses and inversely proportional to the square of the distance between them. Example: In Solar system between sun and other planets. As shown in the figure below, G m1m 2 That is, F g r Where F is ghe gravitational force, m and m1are the 2asses of the two objects and r is 11 2 2 the distance between them. G=6.67 ×10 Nm /kg is universal gravitational constant. Step 2 of 4 The gravitational force exerted by sun on the person is, G M sun F sun = rsunper Where F sunis the force exerted by sun of mass M sunon a person of mass m, who is at a distance of r . sunper The gravitational force exerted by earth on the person is, F = G M earth earth rearthper Where F sunis the force exerted by sun of mass M sunon a person of mass m, who is at a distance of r sunper.