Physics 220 - HW #3 (Homework)

malsaiha::app-6@purdue

Summer-2013-PHYS-22000-01-XLST, Summer 1 2013

Instructor: Shawn Slavin

Current Score : / 20 Due : Tuesday, June 4 2013 11:59 PM EDT

1. /2 points SerCP9 6.P.004.

A ball of mass m is thrown straight up into the air with an initial speed v0.

(a) Find an expression for the maximum height reached by the ball in terms of v0 and g.

hmax =

(b) Using conservation of energy and the result of part (a), find the magnitude of the momentum of the ball at one-half its maximum height in

terms of m and v0.

p =

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WebAssign

2. /2 points SerCP9 6.P.005.

Drops of rain fall perpendicular to the roof of a parked car during a rainstorm. The drops strike the roof with a speed of 16 m/s, and the mass of rain per

second striking the roof is 0.060 kg/s.

(a) Assuming the drops come to rest after striking the roof, find the average force exerted by the rain on the roof.

magnitude N

direction

(b) If hailstones having the same mass as the raindrops fall on the roof at the same rate and with the same speed, how would the average force

on the roof compare to that found in part (a)? (Assume the hailstones bounce back up off the roof.)

The magnitude would be the same as in part (a).

The magnitude would be four times that in part (a).

The magnitude would be half that in part (a).

The magnitude would be double that in part (a).

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3. /2 points SerCP9 6.P.007.

An object has a kinetic energy of 316 J and a momentum of magnitude 25.9 kg m/s.

(a) Find the speed of the object.

m/s

(b) Find the mass of the object.

kg

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4. /2 points SerCP9 6.P.026.

A 68-kg fisherman in a 112-kg boat throws a package of mass m = 15 kg horizontally toward the right with a speed of vi = 4.1 m/s as in the figure

below. Neglecting water resistance, and assuming the boat is at rest before the package is thrown, find the velocity of the boat after the package is

thrown.

magnitude m/s

direction

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5. /2 points SerCP9 6.P.027.WI.

A 68.0-kg person throws a 0.0410-kg snowball forward with a ground speed of 27.0 m/s. A second person, with a mass of 57.0 kg, catches the snowball.

Both people are on skates. The first person is initially moving forward with a speed of 2.20 m/s, and the second person is initially at rest. What are the

velocities of the two people after the snowball is exchanged? Disregard the friction between the skates and the ice.

thrower m/s

catcher m/s

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6. /2 points SerCP9 6.P.034.

A railroad car of mass M moving at a speed v1 collides and couples with two coupled railroad cars, each of the same mass M and moving in the same

direction at a speed v2.

(a) What is the speed vf of the three coupled cars after the collision in terms of v1 and v2?

vf =

(b) How much kinetic energy is lost in the collision? Answer in terms of M, v1, and v2.

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7. /2 points SerCP9 7.P.501.XP.

A race car starts from rest on a circular track of radius 200 m. The car's speed increases at the constant rate of 0.470 m/s2. At the point where the

magnitudes of the centripetal and tangential accelerations are equal, find the following.

(a) the speed of the race car

m/s

(b) the distance traveled

m

( c) the elapsed time

s

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8. /2 points SerCP9 7.P.005.

A dentist's drill starts from rest. After 2.80 s of constant angular acceleration it turns at a rate of 2.1 104 rev/min.

(a) Find the drill's angular acceleration.

rad/s2

(b) Determine the angle (in radians) through which the drill rotates during this period.

rad

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9. /2 points SerCP9 7.P.015.

A car initially traveling eastward turns north by traveling in a circular path at uniform speed as in the figure. The length of the arc ABC is 216 m, and the

car completes the turn in 37.0 s.

(a) Determine the car's speed.

m/s

(b) What is the magnitude and direction of the acceleration when the car is at point B?

magnitude m/s2

direction counterclockwise from the +x-axis

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10./2 points SerCP9 7.P.034.

A satellite has a mass of 90 kg and is located at 1.98 106 m above the surface of Earth.

(a) What is the potential energy associated with the satellite at this location?

J

(b) What is the magnitude of the gravitational force on the satellite?

N

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