1? When the mass of an object is constant. Acceleration is proportional to external force?

2? When the external force is constant. The acceleration of an object is inversely proportional to its mass.

Experimental principle 1, keep the research object? Cars? Is the mass (m) the same? Change the quality of sand in the sand bucket (m)? That is, change the traction to measure the corresponding acceleration of the car? Verify whether acceleration is proportional to acting force by mirror image method.

2. Keep the quality (m) of sand in the sand bucket unchanged? Change the quality of the research object (m)? That is, add or subtract weight in the car? Measure the corresponding acceleration of the car? Verifying whether acceleration is inversely proportional to mass by image method

The experimental equipment is equipped with a long wooden board, a thin wooden pad, a trolley, a thin thread, a small bucket and sand, a dot timer, a low-voltage AC power supply, a conductor and a balance? Bring a set of weights? , millimeter, paper tape and carbon paper, etc.

Experimental steps 1. Measure the mass m0 and M0 of cars and kegs with a balance. And record the values? 2. Install experimental equipment as required? Don't tie the rope hanging the bucket to the car at this time? Just don't add traction to the car? 3. Balance friction? Put a thin board at the end of a long board without a crown block? And move it repeatedly? Until the timer works properly? The movement of the car on the inclined plane can keep the state of uniform linear motion. 4. Record the mass of the car and the added weight in the car? Weigh the sand and pour it into the bucket? Tie the rope to the car and hang the bucket on the crown block? At this point, adjust the height of the crown block so that the rope is parallel to the board? Turn on the power? Let the car go? After setting the timer on the paper tape? Take off the paper tape? Make a mark. 5. keep the total mass of the car unchanged? Change the quality of sand? Weigh with a balance and lay the paper tape according to the method in step 4. Make a mark. 6. Choose an ideal part on each piece of paper? Calculate the acceleration values respectively. 7. Use ordinate to express acceleration? The abscissa represents force? That is, the total gravity mg of sand and sand hopper draws corresponding points according to the experimental results? What if these points are on a straight line? Prove that the quality is positive? The acceleration is proportional to the external force. 8. Keep the quality of sand and buckets unchanged? Put a heavy object in the car? Need to record data, repeat the above experimental steps? Find the corresponding acceleration? Use ordinate to express acceleration? The abscissa represents the reciprocal of the total mass and weight of the car. 1M? Draw corresponding points according to the experimental results? What if these points are on a straight line? Proved that under a certain external force? Acceleration is inversely proportional to mass.

principle

Newton's second law

Law content: the acceleration of an object is directly proportional to the resultant force F and inversely proportional to the mass of the object, and the acceleration direction is the same as the resultant force direction. From the physical point of view, Newton's second law of motion can also be expressed as "the rate at which the momentum of an object changes with time is proportional to the sum of external forces". That is, the first derivative of momentum with respect to time is equal to the sum of external forces. Newton's second law shows that at macro low speed, ∝ f ∝ a and ∝ f ∝ m can be written as ∝ f = KMA by mathematical expression, where k is a constant. However, because the force of 1 unit was not specified at that time, we took k = 1 and got ∑F=ma, which is the expression of Newton's second law that we are familiar with today.