Topic content:
For an object with a mass of m=1.5kg, under the action of horizontal constant force F=15N, the force will be removed after 0.5s from standstill, and the object will continue to slide for a period of time before stopping. The dynamic friction coefficient between the known object and the horizontal surface is μ=0.2, and g is taken as 10m/s2
(1) The acceleration when the constant force acts on the object;
(2) The time for the object to continue sliding after the constant force is removed;
(3) The total displacement of the object from the start to the stop.
Best answer:
(1) Taking m as the research object, the force situation is as shown in the figure: let the acceleration of the object under the action of constant force be a1,
According to Newton's law of motion:
...... (3 points)
(2) The force analysis after the constant force F is removed is shown in the figure. Suppose the speed of the object at the moment when the constant force F is removed
Is v, according to the kinematic formula:...... (1 point)
Assume that after removing the constant force F, the acceleration of the object in uniform deceleration linear motion is a2, and the sliding time is
(3) Suppose that the displacement of the object in uniform acceleration linear motion and uniform deceleration linear motion is s1 and s2 respectively, according to the kinematic formula:
Answer analysis:
slightly
Test core:
force analysis:
1. Methods of force analysis of objects ① Methods: overall method, isolation method.
② Choice: When the physical problem involved is the interaction between the whole and the outside world, the application of the overall analysis method does not need to consider the role of internal forces; When the physical problem involved is the interaction between objects, the isolation analysis method should be applied, and then the internal force of interaction in the original whole will become the external force of each independent object.
2. The sequence of force analysis: first gravity, then contact force, and finally other external forces.
3. Problems that should be paid attention to in force analysis ① When analyzing the force on the object, only the force exerted by the surrounding objects on the research object is analyzed;
② During force analysis, do not apply too much force or omit force. Pay attention to determining the strength object and force bearing object of each force. In the synthesis and decomposition of force, do not regard the actual non-existent resultant force or component force as the force applied to the object;
③ If the direction of a force is difficult to determine, it can be analyzed by hypothesis method;
④ The force condition of the object will change with the change of the motion state, and it can be determined by calculation according to the learned knowledge when necessary;
⑤ The external effect of force analysis should be considered as a whole, and the interaction should be isolated.