1.(1 pt) In physics, a resistive force is a force whose direction is always oppo
ID: 3280451 • Letter: 1
Question
1.(1 pt) In physics, a resistive force is a force whose direction is always opposite to the velocity of the object on which it acts. Which of the following forces is resistive? (Circle all that apply.) Gravity Normal force Friction Buoyant force Tension Air/water resistance 2. You suspend an aluminum (al-2700 kg/m3) cube by a string in a beaker of water(pwater- 1000 kg/m3) so that the top of the cube is a distance d = 3 cm below the surface of water. You've measured the sides of the cube to be a 2 cm. a) (1 pt) Draw a free body diagram for the cube, indicating all the forces acting on it. - b) (3 pts) Find the force of the string on the block (i.e. the tension), both the algebraic expression and the numerical value. c) (3 pts) Assuming that buoyancy and gravity are the only forces acting on the block, what would be the motion of the block if the string were cut? Provide a mathematical representation (i.e. an equation) describing this motion. d) (2 pts) If the uncertainty of your measurement of the side of the cube was 5%, what is the uncertainty in the volume?Explanation / Answer
I am answering the first question according to guidelines.
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A resistive force is a force, whose direction is always opopposite to the velocity of the object.
So here only FRICTION and AIr/water resistance are the resistive forces. They always oppose the motion of object.
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The gravity is the gravitational force of earth. If object is moving away from earth surface then gravity is opposite. When object is moving towards earth surface then gravity is towards it's velocity. Hence it does not always oppose. so not a resistive force always.
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Normal force is supportive force . It is not opposite to velocity of the object. But according to definition of resistive forces, force must be opposing. Hence normal is not resistive.
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Buoyant force is the force applied by water when object is placed in water. It is always upwards towards the surface. whether the object is moving in any direction, buoyant force will be always towards surface. (Not opposite always). Hence not resistive.
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Tension may be opposite or towards the moving object. So not always opposite. Hence not resistive.
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