A block is sliding down a friction compensated runway .Which of the following statements is/are correct?
1)the speed of the block is increasing
2)the normal reaction acting by the runway on the block is increasing
3)the net force acting on the block is zero
a(1) b(3) c(1)(2) d(2)(3)
why the ans is B and why other (1)(2)statements are wrong?can any on EXPLAIN to me?
The question does not explain the meaning of "friction compensated runway". Apparently they mean the slope is adjusted to match the downhill (gravity) and friction vectors so that there is no acceleration.
The confusion in this case is with whoever created that question.
To determine the correct answer, let's break down each statement and analyze it:
1) The speed of the block is increasing.
The correct answer is that the speed of the block is not increasing. As the block is sliding down a friction-compensated runway, it means that the friction force acting on the block is equal to the force pulling it down the slope (likely due to gravity). Since the force of gravity is balanced by the friction force, the block is in a state of equilibrium, and its speed remains constant.
2) The normal reaction acting by the runway on the block is increasing.
This is the correct statement. The normal reaction is the force exerted by a surface perpendicular to the surface. In this scenario, the normal reaction acting on the block by the runway does increase. As the block moves down the slope, it experiences an increased force due to gravity acting in the downward direction. To counteract this force, the runway exerts an equal and opposite normal reaction force, directed perpendicular to its surface. The normal reaction force increases to balance the increased force due to gravity.
3) The net force acting on the block is zero.
This statement is incorrect. The net force acting on the block is not zero since it is experiencing the force of gravity (acting down the slope) and the normal reaction force (acting upward and perpendicular to the surface). The net force is the vector sum of these forces and is not balanced in this case.
Therefore, the correct answer is b(3): Only statement 2, "the normal reaction acting by the runway on the block is increasing," is correct. Statements 1 and (1)(2) are incorrect.
The correct answer is (b) only statement 3) is correct.
Explanation:
1) The speed of the block is increasing: This statement is incorrect. Since there is friction compensating for the sliding motion, it means that the frictional force is acting in the opposite direction to the motion of the block. This force opposes the block's motion and causes it to slow down, not speed up.
2) The normal reaction acting by the runway on the block is increasing: This statement is incorrect. The normal reaction is the force exerted by a surface to support the weight of an object resting on it. In this case, as the block slides down the runway, the normal reaction will remain constant. There is no reason for it to increase.
3) The net force acting on the block is zero: This statement is correct. According to Newton's second law of motion, the net force acting on an object is equal to its mass multiplied by its acceleration. In this scenario, with a friction-compensated runway, the frictional force is equal in magnitude and opposite in direction to the force pulling the block down the runway (typically gravity). As a result, the two forces cancel each other out, resulting in a net force of zero.
So, the correct answer is (b) only statement 3) is correct.