Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action force, identify the reaction force. Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action force, identify the reaction force. The reaction force is zero because the force of the bat on the ball is equal and opposite to the force of the ball on the bat. The reaction force is the force by the ball on the bat. The reaction force is the force of the bat on the ball. The reaction force is the force due to compression inside the ball:

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 ?

When the velocity of an object is doubled, by what factor is its momentum changed? by what factor is its kinetic energy changed? a) the momentum is zero. b) the momentum is not zero. c) difficult to say.

In a voltaic cell, electrons flow from the (positive/negative) to the (positive/negative) terminal.