When landing poorly from a jump, your leg is likely to break at a point just above the ankle where the cross-sectional area of the bone (the tibia) is smallest. The tibia has a radius of 0.70.7cm. A bone will fracture when the compressive stress on it exceeds 130130MPa.

Your intrepid physics instructor (mass 6060kg) jumps from a desktop of height 1.21.2m onto a concrete floor, landing evenly on two legs. How much should she bend her knees to avoid breaking bones? Specifically, what is the minimum stopping distance ddsuch that the stress on the tibia during her landing is sufficiently low that it will not break? Give your answer in cm.

Notice that landing with stiff knees greatly decreases this stopping distance and is thus a really bad idea.

A Sweaty Weight Lifter

In exercising, a weight lifter loses 0.142 kg of water through evaporation, the heat required to evaporate the water coming from the weight lifter's body. The work done in lifting weights is 1.38E+5 J. Assuming that the latent heat of vaporization of perspiration is 2.45E+6 J/kg, find the change in the internal energy of the weight lifter.

The work function for lead is 4.14 eV.

(a) Find the cutoff wavelength for lead.
nm

(b) What is the lowest frequency of light incident on lead that releases photoelectrons from its surface?
Hz

(c) If photons of energy 5.80 eV are incident on lead, what is the maximum kinetic energy of the ejected photoelectrons?
eV

6. A 600 N person sits on a 50 N sled. The coefficient of static friction is 0.14. How much force is needed, respectively, to start the motion by pushing [A] and pulling [B] at an angle of 30°? (Rounding to the nearest integer)

A highway curve with a radius of 450 m is banked properly for a car traveling 80 km/h. If a 1560- kg Porshe 928S rounds the curve at 250 km/h, how much sideways force must the tires exert against the road if the car does not skid?

A factory worker pushes a crate of mass 30.7 kg a distance of 5.00 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and floor is 0.26.

a)What magnitude of force must the worker apply?

b)How much work is done on the crate by this force?

c)How much work is done on the crate by friction?

d)How much work is done by the normal force?

e)How much work is done by gravity?

f)What is the total work done on the crate?

100 kg of R-134a at 200 kPa are contained in a piston–cylinder device whose volume is 12.766 m³. The piston is now moved until the volume is one-half its original size. This is done such that the pressure of the R-134a does not change. Determine the final temperature and the change in the total internal energy of R-134a. Use data from the steam tables.

The final temperature is  °C.

The total change in internal energy is  kJ/kg.

A 330 mLmL soda can is 6.5 cmcm in diameter and has a mass of 21 gg . Such a soda can half full of water is floating upright in water.

What length of the can is above the water level?

(a) A toy car1 has a mass of 1.6 kg and is moving with a velocity of 6.0 m/s to the right. It collides with a second car2 (mass 2.4 kg). The cars stick together. After the collision, both cars move with a velocity of 1.5 m/s to the left.

(a) How fast and in what direction was car2 traveling before the collision?
(b) Calculate the total kinetic energy of the system before and after the collision.

A muon and an antimuon, both with negligible kinetic energy, annihilate each other to produce two photons. The mass of each particle is 1.89×10−28kg, Planck's constant h=4.14×10−15eV⋅s,1eV=1.6×10−19J.

Part A:

Determine the energy in electron volts (eV) of each photon.

Part B:

Determine the frequency of each photon.

Part C:

Determine the wavelength of each photon.

Professor Modyn wants to power his refrigerator with a heat engine. A Carnot heat engine receives heat from a reservoir at 493.0°C at a rate of 767 kJ/min and rejects heat to the ambient air at 29.1°C. The entire work output of the heat engine is used to drive a refrigerator that removes heat from the refrigerated space at -3.23°C and transfers it to the same ambient air at 29.1°C. Note: The IUPAC sign conversion for work is used. Work into the system has a positive value.

a) Determine the maximum rate of heat removal from the refrigerated space (kW)

b) Determine the total rate of heat rejection to the ambient air. Heat rejection is a negative value. Account for both the heat engine and refrigerator. (kW)

A force, in the direction of increasing x, acts on an object moving along the x axis. If the magnitude of the force is F = 10·eN, where x is in meters, find the work done by the force as the object moves from x = 0 to x = 2.0 m

plz answer asap! thank you

On average, both arms and hands together account for 13% of a person's mass, while the head is 7.0% and the trunk and legs account for 80%. We can model a spinning skater with her arms outstretched as a vertical cylinder (head, trunk, and legs) with two solid uniform rods (arms and hands) extended horizontally. Suppose a 75.0 kg skater is 1.60 m tall, has arms that are each 66.0 cm long (including the hands), and a trunk that can be modeled as being 33.0 cm in diameter. If the skater is initially spinning at 79.0 rpm with her arms outstretched, what will her angular velocity ?2 be (in rpm ) after she pulls in her arms and they are at her sides parallel to her trunk? Assume that friction between the skater and the ice is negligble.

A. A ball is launched from ground level, as in the simulation above, with initial velocity components of 40.0 m/s horizontally and 42.0 m/s vertically. Use g = 10 m/s/s, and neglect air resistance.

Exactly 2.00 seconds after launch, what is the angle of the ball’s velocity, measured from the horizontal? _______ degrees

B. A ball is launched from ground level, as in the simulation above, with initial velocity components of 40.0 m/s horizontally and 42.0 m/s vertically. Use g = 10 m/s/s, and neglect air resistance.

What is the range of the ball? We're looking for the horizontal distance from the launch point to the landing point, assuming the ground is completely level. _______ m