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## Homework Statement

32. A 4.0-lb block slides along a horizontal frictionless surface at 8 ft/s. It is brought to rest by compressing a very long spring of spring constant (1/8) lb/ft. The maximum spring compressing is:

A. 4 ft

B. 8 ft (Correct Answer)

C. 16 ft

D. 2 ft

E. 45 ft

33. A block of mass m is initially moving to the right on a horizontal frictionless surface at a speed v. It then compresses a spring of spring constant k. At the instant when the kinetic energy of the block is equal to the potential energy of the spring, the spring is compressed a distance of:

A. v sqrt(m/2k) (Correct Answer)

B. (1/2)mv^2

C. (1/4)mv^2

D. mv^2/4k

E. (1/4)sqrt(mv/k)

34. A 200-lb man jumps out of a window into a fire net 30 ft below. The net stretches 6 ft before bringing the man to rest and tossing him back into the air. The maximum potential energy in (ft*lb) of the net is:

A. 7200 (Correct Answer)

B. 6000

C. 1800

D. 1200

E. 600

## Homework Equations

Emech = K + U

U = 1/2k(x)^2

U = mgh

K = 1/2m(v)^2

## The Attempt at a Solution

32. 1/2 (1/8) x^2 = 1/4 (4) 8^2 <<<< Doesn't work, don't know how I should be setting up the equation.

33. 1/2 kx^2 = 1/2 mv^2

kx^2 = mv^2

x^2 = mv^2/k

x = v sqrt(m/k) <<<< Why am I missing the 2k?

34. mgh = 1/2kx^2

200*32*3 = 1/2*k*6^2

192000 = 18k

k = 10,666.67

U = 1/2 (10,666.67) 6^2 <<<< WAYYYY off.