The force that propels a cannonball when fired from a cannon is
A) huge compared to the recoil force on the cannon.
B) equal and opposite to the force the ball exerts on the cannon.
C) in some cases, equal and opposite to the force the ball exerts on the cannon.
Answer: B
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Equilibrium: A 320-g ball and a 400-g ball are attached to the two ends of a string that goes over a pulley with a radius of 8.7 cm. Because of friction in its axle, the pulley does not begin to rotate. What is the magnitude of the frictional torque at the axle of the pulley if the system remains at rest when the balls are released?
A. 0.068 N ? m B. 0.61 N ? m C. 0.079 N ? m D. 0.063 N ? m E. 0.00070 N ? m
Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10-6 ? ? m at room temperature. What length of No. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature?
A) 3.66 m B) 2.45 m C) 0.61 m D) 6.54 m E) 22.4 m
An object is moving with constant non-zero acceleration on the +x axis. The velocity versus time graph of this object is
A) a horizontal straight line. B) a vertical straight line. C) a straight line making an angle with the time axis. D) a parabolic curve. E) a hyperbolic curve.
Electrical force per unit charge is known as the ________
Fill in the blank(s) with the appropriate word(s).