The string in the figure is 50 cm long. When the ball is released from rest, it

Question

The string in the figure is 50 cm long. When the ball is released from rest, it swings along the dotted arc. How fast is it going at the lowest point in its swing? a. 2.0 m/s b. 3.1 m/s c. 2.2 m/s d. 6.0 m/s e. 4.4 m/s An ideal spring is used to fire a 0.015 block horizontally. The spring has a spring constant of 25 N/m and is initially compressed by 0.05m. The kinetic energy of the block as it leaves the spring is: a. 2.5 times 10^-2 J b. 0 J c. 3.1 times 10^-2 J d. 1.5 times 10^-2 J e. 9.8 times 10^-2 J A golf ball is struck by a golf club and falls on a green A above the tee. The potential the Earth-ball system is greatest: a. the ball reaches the highest point in its flight b. just before the bal struck c. just after the ball is struck d. just after the ball lands on the green e. when the ball comes to rest on the green A 1000kg car starts from rest on a horizontal road and gains a speed of 20m/s in 20 Its kinetic energy and the power required are respectively a. 2 times 10^4 J and 1 times 10^3W b. 1 times 10^5 J and 1 times 10^6W c. 5 times 10^5 J and 1 times 10^3W d. 1.5 times 10^5 J and 1 times 10^5 W e. 2 times 10^5 J and 1 times 10^4 W

Explanation / Answer

4) mgh = 1/2mv^2

v = sqrt(2gh) = 3.13 m/s

5) k = 1/2kx^2 = 1/2*25*0.05^2 = 3.1*10^-2 J

6) at heighest point

7) k = 1/2mv^2 = 2*10^5 J

p = k/t = 10^4 W

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