Question

In the winter sport of curling, players give a 20kg stone a push across a sheet of ice. The stone moves approximately 40m before coming to rest. The final position of the stone in principle only depends on the initial speed at which it is launched and the force of friction between the ice and the stone, but team members can use brooms to sweep the ice in front of the stone to adjust its speed and trajectory a bit; they must do this without touching the stone. Judicious sweeping can lengthen the travel of the stone by 3 m. A) Which of the following statements is correct? The sweepers in a curling competition adjust the trajectory of the stone by decreasing the coefficient of friction between the stone and the ice. The sweepers in a curling competition adjust the trajectory of the stone by increasing the coefficient of friction between the stone and the ice. The sweepers in a curling competition adjust the trajectory of the stone by changing friction from kinetic to static. The sweepers in a curling competition adjust the trajectory of the stone by changing friction from static to kinetic. B)Suppose the stone is launched with a speed of 3 m/s, and travels 40m before coming to rest.What is the approximate magnitude of the friction force on the stone? 0 N 2 N 20 N 200 N C)Suppose the stone's mass is increased to 37kg , but it is launched at the same 3m/s . Which one of the following is true? The stone would now travel a longer distance before coming to rest. The stone would now travel a shorter distance before coming to rest. The coefficient of friction would now be greater. The force of friction would now be greater. Its my only problem left and I am confused on how to work them. Detail is a 5 star!

Answer 1

The sweepers d. Decreasing the coefficient of friction between the stone and the ice. Since frction opposes the relative motion ofanyobject, when it is decreased, the object in a curling competition a djust the trajectory of the stone by can travel some more distance. The stone undergoes a de-acceleration as it stops after travelling 40nm The acceleration of the stone is as follows: - 2as 0* -(3 m/s)2a40 m ad 80 a--0.113 m/s The force acting on the stone is as follows: -(20 kg) (0.113 m/s) -2.25 N This force is balanced by the static friction when the stone stops, so that the frictional force is as follows: f,-2.25N The mctional force is approximately 225 N.

The frictional force is given by the following expression: The initial velocity ofthe motionis same an on the mass ofthe stone. Thus, the stone travels the same distance as it did when its mass was 20 kg. So option (a) and (b) are not correct. dacceleration is same as it is not dependent The coefficient of fiction depends only on the nature of materials in contact and not on the size andmass ofthe objects. Thus, the coefficient of friction carmot increase. Hence, option (c)is not comect The force of friction is dependent on the mass of the object so that on increasing the mass, friction will increase. Thus, the conmect option is (d).