13. Suppose the force is applied at an angle. At what angle should the force be

Question

13. Suppose the force is applied at an angle. At what angle should the force be applied to achieve the largest possible speed after the block has moved 1.9 m to the right (1.5pt) a. 8.0° b. 6.0° c. 5.0° d. 9.0° J) An elevator car has a mass of 1800 kg and is carrying passengers having a combined mass of 200 kg. A constant friction force of 4000 N retards its motion. 14. How much power must a motor deliver to lift the elevator car and its passengers at a constant speed of 3.00 m/s(1 pt) a. 3.50x104 w b. 5.90x104 w c. 7.08x10 w d. 4.68x10 w K) The launching mechanism of a popgun consists of a trigger- released spring. The spring is compressed to a position ya and the trigger is fired. The projectile of mass m rises to a position yc above the position at which it leaves the spring. Consider a firing of the gun for which m = 25.0 g, yh=-0.10 m, and ye-20.0 m. 15. Neglecting all resistive forces, determine the spring constant(1 pt) a. 492 N/m b. 98.5 N/m c. 985 N/m d. 980 N/m 16. Find the speed of the projectile as it moves through the equilibrium position B of the spring '1 pt) a. 16.5 m/s b. 19.8 m/s c. 19.6 m/s d. 19.4 m/'s LI A block of mass m 2.00 kg is attached to a spring of force constant k 500 N/m. The block is pulled to a position x, -4.00 cm to the right of equilibrium and released from rest.

Explanation / Answer

J) Fnet = F - m g - f = 0

F = (1800 + 200)(9.81) + 4000 = 23620 N

P = F.v = 70860 W Or 7.08 x 10^4 W

Ans(C)

K) (15). Applying energy conservation,

k x^2 /2 = m g h

k (0.10^2) /2 = (0.025) (9.80)(20 + 0.10)

k = 984.9 N/m

Ans. (C)

(16). Work done by spring + work done by gravity = change in KE

- 0.025 x 9.8 x 0.10 + 984.9 x 0.10^2 / 2 = 0.025 v^2 / 2

v = 19.8 m/s

Ans(b)

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