Physics
it is estimated that 1.0 kg of body fat will provide
3.8 × 107 j of energy. a 60-kg mountain climber decides
to climb a mountain 4000 m high.
(a) how much work does the climber do against
gravity in climbing to the top of the mountain?
the answer for this is 2.4x10^6
(b) if the body’s efficiency in converting energy stored as
fat to mechanical energy is 25%, determine the
amount of fat the climber will use up in providing the
energy required to work against the force of gravity.
the answer is 0.25kg
i got a) but i don't understand how to do b)

The velocity of car is 80.0 miles per hour. what is the velocity of car in meters per second? (1 km -0.621 miles) m/s

Aparticle of mass m is projected with an initial velocity v0 in a direction making an angle α with the horizontal level ground as shown in the figure. the motion of the particle occurs under a uniform gravitational field g pointing downward. (a) write down the lagrangian of the system by using the cartesian coordinates (x, y). (b) is there any cyclic coordinate(s). if so, interpret it (them) physically. (c) find the euler-lagrange equations. find at least one constant of motion. (d) solve the differential equation in part (c) and obtain x and y coordinates of the projectile as a function of time. (e) construct the hamiltonian of the system, h, and write down the hamilton’s equations (canonical equations) of motion.

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative