According to the work-energy theorem, Wnet=ΔKWnet=ΔK. Consider a weightlifter lifting a barbell above their head and keeping it stable (i.e. not moving), in a configuration similar to the picture of a female weightlifter below:       Does the weightlifter exert any work on the barbell? If so, does the weightlifter expend energy during this process? Justify your answer using the work-energy theorem and/or descriptions of free-body diagrams

If object B also has 24 J of kinetic energy, is it moving faster or slower than object A? Find the ratio of the speeds of objects A and B. By what factor does the speed of each object change if total work -12 J is done on each?

On an essentially frictionless, horizontal ice rink, a skater moving at v = 3.0 m/s encounters a rough patch that reduces her speed to 45% due to a friction force that is 25% of her weight (w). Use the work-energy theorem to find the length of this rough path.Express first your answer in terms of any or all of the variables v, w, and g (acceleration due togravity), and then its numerical value

A car with mass 1520 kg is traveling down the highway at a speed of 18 m/s when the driver slams on the brakes due to an accident up ahead. The car eventually comes to rest.According to the work-energy theorem the work is related to the change in kinetic energy, Wnet = Δ KE = KEfinal - KEinitial.(a) Using the work-energy relationship, determine how much net work is done on the car from the brakes? Report the magnitude of the the work (positive value) even though the work from brakes will be negative since the car is slowing down._____ J(b) The brakes apply a force of 24000 N to the car in order to make it stop. Using the fact that W = F d and the fact that the you found the work done (magnitude) by the brakes in part (b), determine the stopping distance, d, of the car.____ m