Physics problems: dynamics

Part 4



Problem 31.

A circus clown weighs 900 N. The coefficient of static friction between the clown's feet and the ground is 0.4. He pulls vertically downward on a rope that passes around three pulleys and is tied around his feet. What is the minimum pulling force that the clown must exert to yank his feet out from under himself?



Problem 32.

The athlete, who has a mass of 100 kg, can throw a 500 g ball with a speed of 10 m/s. The distance through which his hand moves as he accelerates the ball forward from the rest until he releases it is 1.0 m. What constant force must the athlete exert on the ball to throw it with this speed?



Problem 33.

When a falling object is at a distance above the Earth's surface of 4 times the Earth's radius, what is its free-fall acceleration due to the Earth's gravitational force exerted on it?



Problem 34.

A 10.0 kg block is towed up an inclined at with respect to the horizontal. The rope is parallel to the incline and has a tension of 100 N. Assume that the block starts from rest at the bottom of the hill, and neglect friction. How fast is the block going after moving 40 m up the hill?



Problem 35.

A 0.01 kg object is moving in a plane. The x and y coordinates of the object are given by and y . Find the net force acting on the object at t=2 s.





Problem 36.

An automobile weighing 3200 lbs. is on a road which rises 10 ft. for each 100 feet of road. What force tends to move the car down the hill?



Problem 37.

At 20 meters long rope attached at the top and the bottom of a flag pole is pulled 2 meters away from the pole by a 100 newton force acting at right angles to the pole at its mid point. What is the tension on the segments of the rope on each side of the 100 newton force?



Problem 38.

A crane cable that is capable of withstanding 22,000 N is attached by a hook to  a 2,000 kg block that is resting on the ground. The cable initially starts lifting the block at the maximum acceleration that the cable can withstand for 4 sec.  It then continues to raise the block at constant velocity for further 2 sec. At this time the block slips off the hook at the end of the cable.

(1) the tension in the cable when the block is moving at constant velocity;

(2) the maximum acceleration that the cable can withstand;

(3) the maximum height that the block reaches above ground.



Problem 39.

A body of mass 10g is set to rotate in a circular path by means of a string 200 cm long. If it makes 3 complete revolutions in 2s, find the tension of the string.



Problem 40.

A particle moves in a circle of radius 1 m. Its linear speed is given by , where t is in second and v in meter/second. Find the radial and tangential acceleration at .








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