#1) A child ties a .25kg rock to the end of a string and whirls it at a constant speed in a horizontal circle of radius 75 cm. What, approximately, is the maximum speed at which the stone may be whirled if the string will break for a tension exceeding 300N? A. 10 m/s B. 13 m/s C. 15 m/s D. 20 m/s E. 30 m/s I'm getting like 51 on this one so I must be doing something wrong. #2) The gravitational force on the moon due to the Sun is about twice the gravitational force on the Moon due to the Earth. The Moon isn't pulled away from the Earth by the Sun because A. it is much closer to the Earth than to the Sun. B. the net force on it is zero. C. both the Moon and the Earth accelerate together around the Sun. D. all of the above E. None of the above. A and C both sound right. Is the net force on it zero though? I guess so right? So C? #3) A car towing a trailer accelerates up a hill. Which one of the following statements is true? A. The car exerts a smaller force on the trailer than the trailer exerts on the car. B. The car exerts the same force on the trailer as the trailer exerts on the car. C. The car exerts a greater force on the trailer than the trailer exerts on the car. D. The relationship between the force exerted by the car on the trailer and the force exerted by the trailer on the car depends on the acceleration of the trailer. E. The relationship between the force exerted by the car on the trailer and the force exerted by the trailer on the car depends on the mass of the trailer. B. They are equal right? #4) The coefficients of kinetic and static friction between a 3.0 kg crate and the florr on which it rests are .30 and .40 respectively. If the crate is initially at rest, what is the magnitude of the net force on the crate when a 6.0 N horizontal force is applied? A. 0.0 N B. 2.8 N C. 5.8 N D. 6.0 N E. 17 N It's A right? Because the normal force on the box is 29.4 N and then multiplied by static friction is 11.76 N so you would need to exert more than that to move the box. So if it's not moving, the net force is 0 right?