A worker pushes a crate up a ramp Which change to the ramp would be the best way to increase its mechanical
efficiency (ME), and why?
O A. Reduce the length of the ramp so that more work is done in less
time.
O B. Wax the sloped surface of the ramp to decrease the friction
between the crate and the ramp.
O c. Cover the ramp with sandpaper to increase the friction between
the crate and the ramp.
O D. Reduce the height of the ramp so that less output work is done on
the crate.

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

Very large accelerations can injure the body, especially if they last for a considerable length of time. one model used to gauge the likelihood of injury is the severity index ( ), defined as =/ . in the expression, is the duration of the accleration, but is not equal to the acceleration. rather, is a dimensionless constant that = the number of multiples of that the acceleration is equal to. in one set of studies of rear-end collisions, a person's velocity increases by 13.7 km/h with an acceleration of 36.0 m/s2 . let the + direction point in the direction the car is traveling. what is the severity index for the collision?

Two resistors r1 and r2 may be connected either in series or parallel across an ideal battery with emf ε. we desire the rate of energy dissipation of the parallel combination to be 8.75 times that of the series combination. if r1 = 105 ω, what are the (a) smaller and (b) larger of the two values of r2 that result in that dissipation rate?