A 40-kg crate is being lowered with a downward acceleration is 2.0 m/s2 by means of a rope
(a) What is the magnitude of the force exerted by the rope on the crate?
(b) What would be the magnitude of the force exerted by the rope if the crate were being raised with an acceleration of 2.0 m/s2?
(a) 310 N (b) 470 N
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A refrigerator extracts 65 J of heat from a heat reservoir at
If the coefficient of performance of the refrigerator is 2.5, then how much work is needed to run the refrigerator?
A. 26 J B. 48 J C. 75 J D. 90 J
When a 20-V emf is placed across two resistors in series, a current of 2.0 A is present in each of the resistors. When the same emf is placed across the same two resistors in parallel, the current through the emf is 10 A. What is the magnitude of the greater of the two resistances?
A. 7.2 ? B. 7.6 ? C. 6.9 ? D. 8.0 ? E. 2.8 ?
A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later?
A) 50 m B) 98 m C) 100 m D) 490 m E) none of the above
The Sgr A* black hole may contain three million solar masses
Indicate whether the statement is true or false