At the Beijing Olympics a Chinese female weightlifter set a new world record. She lifted 117 kg, holding it stationary for a specified time. Her own mass was 47kg. Assume that before the attempt, the centre of mass of the bar and “weights” combined was 0.15 m above the floor, and while she was holding the bar aloft, its centre of mass was 1.65 m above the floor. How much work did she do on the bar and weights during the attempt? a.How much work did she do on the bar and weights during the attempt? b.Assuming the lift took 0.2s to complete, what was her power output during the lift?

Sally throws a puck of mass m = 0.20 kg with an initial velocity i = 5.00å m/s along a horizontal frictionless ice surface towards the net. The goalie exerts a constant force, F, with his hand when making the save by bringing the puck to rest before it goes in the net. During the save, his hand moves back by a distance d = 0.50 m. What is the magnitude and direction of F? (A) F = 0.00 N (no force is required) (B) F = -1.00 N (C) F = +1.00î N (D) F = -5.00î N (E) F = +5.00î N (F) F = -10.08 N (G) F = +10.02 N

An object with a mass of 56.0 kg is fired with an initial speed of 1.40  102 m/s at an angle of 30.0° above the horizontal from a 142 m high cliff (take ground level to be y = 0 m). (a) Determine the initial total mechanical energy (in J) of the system of the projectile and the earth.  Can you express the initial total mechanical energy of the object-earth system in terms of the initial kinetic energy of the object and potential energy of the system? Can you write expressions for the initial kinetic energy of the object and potential energy of the system? J (b) If when the projectile is at its maximum height of y = 346 m, it is traveling 99.2 m/s, determine the amount of work (in J) that has been done on the projectile by air resistance.  Can you obtain an expression for the total energy of the system at the object's maximum height? Can you write an expression for the work done on the object by air resistance as it travels to the top of its trajectory in terms of the total energy…

1) In the formula given for the calculation of work, the variable F represents: A) The angular coordinate of the vector d when it is written in polar coordinates B) The scalar magnitude of the force doing work C) The angular coordinate of the vector F when it is written in polar coordinates D) The scalar magnitude of the displacement through which the system moves while the force isapplied E) The direction of the force acting on the system F) The angular difference between the vectors F and d G) The diameter of the system H) The weight, or force due to gravity, on the system I) The work done by the force F 2) In the formula given for the calculation of work, the variable d represents: A) The angular coordinate of the vector d when it is written in polar coordinates B) The scalar magnitude of the force doing work C) The angular coordinate of the vector F when it is written in polar coordinates D) The scalar magnitude of the displacement through which the system moves while the force…

A cord is used to vertically lower an initially stationary block of mass M = 4.9 kg at a constant downward acceleration of g/7. When the block has fallen a distance d = 2.4 m, find (a) the work done by the cord's force on the block, (b) the work done by the gravitational force on the block, (c) the kinetic energy of the block, and (d) the speed of the block. (Note : Take the downward direction positive) (a) Number Units (b) Number Units (c) Number Units (d) Number Units

Problem 4: During an ice show, a 67.5-kg skater leaps into the air and is caught by an initially stationary 82.5 kg skater. Part (a) What is their final speed, in meters per second, assuming negligible friction and that the 67.5 kg skater's initial horizontal speed is 4.25 m/s? Numeric : A numeric value is expected and not an expression. v'= Part (b) How much kinetic energy is lost, in joules? Numeric : A numeric value is expected and not an expression. ΔΚΕ10st Ξ

A tired squirrel (mass 1 kg) does push-ups by applying a force to elevate its center-of-mass by 5 cm. Determine the number of push-ups which a tired squirrel must do in order to do a mere 1.0 Joule of work.

A 5.24 kg object falls freely (ignore air resistance), after being dropped from rest. Determine the initial kinetic energy (in J), the final kinetic energy (in J), and the change in kinetic energy (in J) for the following.

A 10.0-kg bob is attached to a rod whose length is 10.0 m. The right end of the rod is fixed, and the bob is released from rest. a) Determine the speed of the bob when it is below the pivot point (vertical angle is zero). b) Determine the tension in the rod when the bob is below the pivot point. hint: to determine the speed of the bob when it is below the pivot point, you will need to use Calculus.

You overindulged on a delicious dessert, so you plan to work off the extra calories at the gym. To accomplish this, you decide to do a series of arm raises holding a 5.5 kg weight in one hand. The distance from your elbow to the weight is 38 cm, and in each arm raise you start with your arm horizontal and pivot it until it is vertical. Assume that the weight of your arm is small enough compared with the weight you are lifting that you can ignore it. As is typical, your muscles are 20 % in converting the food energy they use up into mechanical energy, with the rest going into heat. If your dessert contained 350 food calories, how many arm raises must you do to work off these calories?