1. The gravitational force exerted by the Sun on the Earth causes the Earth to o
ID: 2029683 • Letter: 1
Question
1. The gravitational force exerted by the Sun on the Earth causes the Earth to orbit about the Sun. Assume that the orbit is perfectly circular. The work done by this gravitational force during a small displacement of the Earth along is orbital path is (a) zero (b) positive (c) negative (d) impossible to determine. 2. The figure shows four examples of a force applied to an object. In all cases, the force has the same magnitude, and the displacement of the object is to the right and of the same magnitude. Rank the situations in order df the work done by the force, from most positive to negative: 3. A dart is inserted into a spring- loaded dart gun by compressing the spring in by a distance x. For the next loading, the spring is compressed a distance 2x. How much work is required to load the second dart compared with the first? (a) four times as much (b) twice (c) the same (d) one-half (e) one-quarter How much faster does the second dart leave the gun compared with the first? (a) four times as fast (b) two times (c) the same (d) one-half (e) one-quarter 4. Choose the correct answer. The gravitational potential energy of a system (a) is always positive (b) is always negative (c) can be negative or positive 5. If the net work done by external forces on a particle is zero, mark which of the following statements about the particle must be true (a) Its velocity is zero (b) Its velocity is decreased (c) Its velocity is unchanged (d) Its speed is unchanged (e) More information is needed 6. What does the slope of a graph of u(x) versus x represent? (a) the magnitude of the force on the object (b) the negative of the magnitude of the force on the object (c) the x component of the force on the object (d) the negative of the x component of the force on the objectExplanation / Answer
1 ) work done is zero as the motion of the earth and the force of gravity from sun are perpendicular to each other. Work is therefore zero as work is W = F*S , where S is the distance travelled in the direction of the force, as they are perpendicular to each other, distance and force are not in the same line, this product is zero.
2) In diagram a, there is zero work done by force, In diagram b, there is negative work done by force as force and displacement are in opposite direction, In diagram c, force is maximum (positive) as force and displacement are in same direction and are parallel, In diagram d, force will be resolved into components and will be less positive than diagram c.
3) it will take 4 times as much work
as dart will have 4 times the kinetic energy, it will leave the gun at two times faster.
4) it can be negative or can be postivie , depends upon our reference
5) Only option d is ture, as Velocity is the rate of change of displacement of a particle in a certain direction.
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