Question

True or False:

1. The force in work is the magnitude of the constant force. T________ F______
2. When pulling a chest across the floor with a rope tied to the end, the work increases as the angle decreases towards the horizontal plane of the floor. T_______ F________
3. The less the displacement of the apple when pushed across the desk, the less work that is done. T_____F_____
4. The work to push the same chair across a surface of 10 m in distance, is the same on ice as it would be on glass. T_____F_____
5. As an object in space orbits in a perfect circle around another object, the work done is 0. T____F_____
6. Kinetic energy is created when an object is experiencing a velocity equal to zero. T____F____
7. The total work done on an object by all of the forces acting on it, equals the change in the objects kinetic energy. T_____F_____
8. Relative modest increases in the speed of an object can lead to rather large increases in its kinetic energy. T_____F_____
9. The potential energy increases as an object is placed closer to the earth’s surface. T_____F_____
10. The energy to run a 60 W lightbulb for 6.9 second is 8.7 Joules. T_____F______
11. 11) Efficiency increases when the total energy out increases. T_____F_____

Answer 1

1. True

The force in work is always the magnitude of constant force. However sometimes force doesnot remain constant during the work along a particular displacement/distance. In that case the displacement/distance is divided in infinitely small elements so that force remains constant over that element. The work is calculated over that element and then whole work is calculated by integrating this small work.

2. True

W = Fscosθ

if θ increases, cosθ decreases so does the work

so if angle increases work done decreases.

3. True

Since workdone W = FScosθ

clearly workdone is directly proportional to S (displacement)

so if the displacement in apple is less, less work is done