2. Could you tell me what the word magnitude means in terms of physics and also could you write a word equation which defines the magnitude of a force.
3. What is the unbalanced force required to accelerate a 2.0 kg mass at 4.0 ms-2?
4. Why is it said that we are in motion in a moving bus when no type of force or energy is used by us?
5. In a vacuum-sealed universe, an elephant and a feather are pushed off a cliff at the SAME time. Which one lands first and why?
6. If an object is dropped from two different hieghts, will the speed/power change?
e.g., We drop a penny off a twenty foot ladder, then drop a penny off the empire state building. Will it be more powerful and/or faster?
7. (i) Does a body's ability to withstand force depends on its density? I have come up with an assumption to explain why man cannot rest on snow. If it is wrong please tell me. As the body exert a force on the snow, the snow exerts a force on the body. However,the force exert on the snow is too much for the snow, and as a result it will give way to the body. As the body loses contact with the snow, there is no more upward force exerted on the body, and as a result the body falls and sinks into the snow, but why is the snow not able to withstand the weight? Is it because of density? The density of the snow is smaller, that's why there are more atoms exerting force than the atoms of the snow receiving the force, so the snow give way to the body? Is my assumption true? When a body is falling, the air resistance equals the force exerted by the body on the air, f, unless in terminal velocity, f is not equal to weight of the body. Why is this so?
(ii) I think you have answered my question on snow earlier on, but the problem is I don't understand and cannot relate it to Newton's third law. Because to remain in static equilibrium, upward and downward force are the same, since we sink in snow, the downward force should be greater than the upward force. The reason why the downward force is more than the upward force is because the snow cannot exert anymore upward force on the body. The snow cannot exert the force on the body is because it has given way to the body as snow cannot withstand the body's weight. When a body falls, I understand that air resistance is always less than the weight unless in terminal velocity, but air resistance is the force exerted by the body on the air. Shouldn't this force, which is the reaction to air resistance, be equal to the weight of the body?
8. (i) I need to teach the student about Newton's Law in the coming two month. So, I'm planning some simple experiments or activities, they can use in teaching. I find that it is difficult in planning the simple experiments or activities in teaching Newton's Third Law. So, can someone send me useful ideas/suggestion in teaching Newton's Third Law? (ii) What is the reaction force to a body's weight in free fall?
9. In theoretical physics, would Star Trek' inertial dampeners be possible?
10. Alicia and Betty are studying on their table in their physics classroom. In response to Betty's query, Alicia slides her 1.5 kg book towards Betty (who is sitting to Alicia's left) with a force of 9.5 N. If the force of friction between the book and the table is 7 N, what is the book's acceleration?
11. A box of bananas of mass 2.5 kg rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.40, and the coefficient of kinetic friction is 0.20. (a) If a monkey applies no horizontal force on the box and the box is at rest, what is the force of friction on the box? (b) What is the magnitude of the force of friction if the monkey applies a horizontal force of 7.0 N to the box and the box is initially at rest? (c) What minimum horizontal force must the monkey apply to start the box in motion? (d) What minumum horizontal force must the monkey apply to keep the box moving at constant velocity once it has been started? (e) If the monkey applies a horizontal force of 15.0 N, what is the acceleration of the box?
12. A person stands on bathroom scales that rest on the floor of an elevator (lift). When the elevator is stationary, the scales register 50 kg. When the lift accelerates upwards the scales register 60 kg. Taking the acceleration of gravity to be 10 ms-2, the best estimate for the acceleration of the lift is:
A 100 ms-2 B 11 ms-2 C 8 ms-2 D 2 ms-2
13. A stone of mass 80 g is released at the top of a vertical cliff. After falling for 3 s, it reaches the foot of the cliff, and penetrates 9 cm into the ground. What is: (a) the height of the cliff, (b) the average force resisting penetration of the ground by the stone?
14. A railway engine of mass 100 tons is attached to a line of trucks of total mass 80 tons. Assuming there is no resistance to motion, find the tension in the coupling between the engine and the leading truck when the train: (a) has an acceleration of 0.020 m/s2, (b) is moving at constant velocity. (1 ton = 1000 kg = 1 x 103 kg).
15. In a tug-of-war between 13 students and five parents, the 13 students (with an average mass of 50 kg each) pull westward on a rope with an average force of 150 N per student. The five parents (with an average mass of 80 kg each) pull eastward on the other end of the rope with an average force of 475 N per parent. Assuming that the whole mass accelerates together as a single entity, what is the acceleration of the system?
16. A body of mass 5 kg is acted upon by two perpendicular forces of 8 N and 6 N. What is the magnitude and direction of the acceleration of the body?
17. Two objects or masses 3 kg and 2 kg respectively are connected by a light string over a frictionless pulley. Calculate (a) the acceleration of the system and (b) the tension in the cord (g = 10 m/s2).
18. Is it easier to pull or push an object? Why?