A pendulum of mass 12 kg is released from rest at some height, as shown by point A in the image below. At the bottom of its arc at point B, it is traveling at
a speed of 19 m/s. What is the approximate amount of energy that has been
lost due to friction and air resistance? (Recall that: g = 9.8 m/s2)

Space-time metric ds2= -dt2+at2dx2+bt2dy2+ct2dz2 (a)how does the area of a rectangle with vertices at ( x=0, y=0, z=0 ), (1,0,0 ), ( 0,1,0 ) and (1,1,0 ) changes with time? (b) if a photon moving in the x direction starts from the origin at t=1, when does it reach x=l? (ds=0 for the trajectory of a photon.) (c) the proper time for a particle is defined by cd=ds. what is the proper time for a particle to move along the trajectory ( x(t)=t, y(t)=0, z(t)=0 ) from t=0 to 1 ? what is the condition on the parameter a so that the velocity of the particle never exceeds the speed of light ?

True or false: the cycle of seasons on the earth is caused by the tilt of the earth on its axis toward and away from the sun.

Aperson standing in a canoe exerts a force of 700 n to throw an anchor over the side. find the acceleration of the canoe if the total mass of the canoe and the person is 100 kg?