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July 24, 2014

July 24, 2014

Posted by **physicsclass** on Saturday, April 16, 2011 at 5:45pm.

A boat with a horizontal tow rope pulls a water skier. She skis off to the side, so the rope makes an angle of 15.0 degrees with the forward direction of motion. If the tension in the rope is 180 N, how much work does the rope do on the skier during a forward displacement of 300.0 m?

A 715 N person walks up three flights of stairs, covering a total vertical distance of 10.5 m. (a) If, as is typical, only 20% of the caloric (food) energy is converted to work by the muscles, how many joules and food calories of energy did the person use? (One food calorie=4186 J.) (b) What happened to the other 80% of the food energy?

A 0.420 kg soccer ball is initially moving at 2.00 m/s. A soccer player kicks the ball, exerting a constant 40.0 N force in tbe same direction as the ball's motion. Over what distance must her foot be in contact with the ball to increase the ball's speed to 6.00 m/s?

A 1200 kg car is moving on the freeway at 65 mph. (a) Find the magnitude of its momentum and its kinetic energy in SI units. (b) If a 2400 kg SUV has the same as the 1200 kg car, how much momentum and kinetic energy does it have?

The magnitude of the momentum of a cat is p. What would be the magnitude of the momentum (in terms of p) of a dog having three times the mass of the cat if it had (a) the same speed as the cat, and (b) the same kinetic energy as the cat?

On a highly polished, essentially frictionless lunch counter, a 0.500 kg submarine sandwich moving 3.00 m/s to the left collides with an 0.250 kg grilled cheese sandwich moving 1.20 m/s to the right. (a) If the two sandwiches stick together, what is their final velocity? (b) How much mechanical energy dissipates in the collision? Where did this energy go?

A catcher catches a 145 g baseball traveling horizontally at 36.0 m/s. (a) How large an impulse does the ball give to the catcher? (b) If the ball takes 20 ms to stop once it is in contact with the catcher's glove, what average force did the ball exert on the catcher?

A 0.300 kg glider is moving to the right on a frictionless, horizontal air track with a speed of 0.80 m/s when it makes a head-on collision with a stationary 0.150 kg glider. (a) Find the magnitude and direction of the final velocity of each glider if the collision is elastic. (b) Find the final kinectic energy of each glider.

- physics -
**MAHARSHI**, Friday, August 5, 2011 at 3:25amANSWER 3P

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