A 150-g ball is fired from the edge of a 20-m tall building with an initial velo

Question

A 150-g ball is fired from the edge of a 20-m tall building with an initial velocity of v_0 = 34.2 m/s directed 30 degree above horizontal. The projectile rises to point P and then on ground at Q. (a) Determine flight time of the projectile as it lands at Q. (b) Find how far from the base of building the projectile lands. (c) Calculate the gravitational potential energy of the projectile at point P. 0.5-kg piece of a metal (specific heat unknown) having a temperature of 100 degree C is added to 150-g of water (specific heat 4190 j/kg-C) having a temperature of 10 degree C in a Styrofoam cup (negligible specific heat.). The final equilibrium temperature of the system is 24 degree C. (a) Find specific heat of the metal. (b) Determine quantity of heat absorbed by water.

Explanation / Answer

5. (A) in vertical its displacement is - 20 m as it reaches to Q.

y = - 20 m

v0y = 34.2 sin30 = 17.1 m/s

Applying y = v0y t + ay t^2 / 2

- 20 = 17.1 t - 9.8 t^2 /2

4.9 t^2 - 17.1 t - 20 = 0

t= 4.41 sec

(B) x = v0x t

= (34.2 cos30) (4.41)

= 130.6 m

(C) PE at P = total energy at launch point

= (0.150 x 9.8 x 20) + (0.150 x 34.2^2 / 2)

= 29.4 + 87.7

= 117.1 J

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