物理牛顿定律英文版
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The remaining question is ,even though Stephen slammed on the brake, the accident happened anyway. What caused this tragedy??
According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
While the elevator accelerates upward, the apparent weight of the fish is greater than its true weight, mg.
The forces on the fish are again shown in the free-body diagram
Newton’s first law of motion牛顿第 一定律:
Every body continues in its state of uniform motion or rest unless acted up on by an external force
Application of the Newton’s first law
Now that we know Newton's Laws of Motion, how do we apply them? How can they let us predict the motion of an object if we know all the forces acting upon it? How can they let us predict the forces on an object if we know its motion?
One day ,Stephen Su was driving a motorcycle on the street. Meanwhile, David was driving a trunk at a fast speed.
பைடு நூலகம்
Stephen Su did not stop in time as soon as the traffic light turned red. David could not control the van and collided with Stephen.
Fnet = T - mg
The net force is (always!) equal to the mass times the acceleration. This fish is moving along with the elevator. Now the acceleration to be up so it is negative.
Example 1: Consider a crate being pulled along a horizontal, frictionless floor. A rope is tied around it and a man pulls on the rope with a force of T. T is the tension in the rope. What happens to the crate?
Safety belts Any passengers in the car will also be decelerated to rest if they are strapped to the car by seat belts. Being strapped tightly to the car, the passengers share the same state of motion as the car. As the car accelerates, the passengers accelerate with it; as the car decelerates, the passengers decelerate with it; and as the car maintains a constant speed, the passengers maintain a constant speed as well.
A disk and a hoop of the same mass M and radius R roll without slipping across a horizontal floor. Both the disk and the hoop are moving with velocity v when the floor starts to slope upward. Which statement is correct? ( )
The net force is (always!) equal to the mass times the acceleration. This fish is moving along with the elevator. In this diagram we have taken the acceleration to be up so it is positive. Fnet = T - m g = m a T = m g+ m a T = m (g + a)
Newton's Second Law tells us that rate of increase (or decrease) in the speed of something which is moving is proportional to the force acting on it. Imagine that you are riding a bicycle along a perfectly smooth and level road and you decide to stop pedaling. If there is a strong wind pushing against you, you will stop completely in a shorter time than you would if the wind was light.
1. Who was the scientist who gave us the Laws of Motion? Answer: Sir Isaac Newton 2. How many Laws of Motion are there? Answer: three 3. What is another name for the first law of motion? Answer: Law of Inertia 4. Which law explains why we need to wear seat belts? Answer: First Law of Motion
(a) The disc makes it to a greater height than the hoop. (b) The hoop makes it to a greater height than the disk. (c) Both the disk and the hoop make it to the same height.
Answer = 50 newtons
Example 2:
This particular example is stated in terms of weighing a fish in an accelerating elevator. It is also fun to think of weighing yourself in an accelerating elevator. When does an elevator accelerate upwards? When does an elevator accelerate downwards?
Fnet = F = T + n + w Fnet, x=F x=Tx+n x+ w x Fnet,y =Fy=Ty+ ny+ w y
n=w
Newton's Second Law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
(a) The disc makes it to a greater height than the hoop. (b) The hoop makes it to a greater height than the disk. (c) Both the disk and the hoop make it to the same height.
or
FORCE = MASS times ACCELERATION
Kobe's car, which weighs 1,000 kg, is out of gas. Kobe is trying to push the car to a gas station, and he makes the car go 0.05 m/s2. Using Newton's Second Law, you can compute how much force Kobe is applying to the car.
These forces are shown on the "free body diagram" above. We have drawn in all the forces acting on the object. The net force is the vector sum of these forces.
A disk and a hoop of the same mass M and radius R roll without slipping across a horizontal floor. Both the disk and the hoop are moving with velocity v when the floor starts to slope upward. Which statement is correct? ( b )
The forces acting on the fish are shown in the free-body diagram. T is the tension supplied by the scale. This is the value the scale reads. We may call it the apparent weight of the fish. The net force on the fish is Fnet = T - mg
According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
While the elevator accelerates upward, the apparent weight of the fish is greater than its true weight, mg.
The forces on the fish are again shown in the free-body diagram
Newton’s first law of motion牛顿第 一定律:
Every body continues in its state of uniform motion or rest unless acted up on by an external force
Application of the Newton’s first law
Now that we know Newton's Laws of Motion, how do we apply them? How can they let us predict the motion of an object if we know all the forces acting upon it? How can they let us predict the forces on an object if we know its motion?
One day ,Stephen Su was driving a motorcycle on the street. Meanwhile, David was driving a trunk at a fast speed.
பைடு நூலகம்
Stephen Su did not stop in time as soon as the traffic light turned red. David could not control the van and collided with Stephen.
Fnet = T - mg
The net force is (always!) equal to the mass times the acceleration. This fish is moving along with the elevator. Now the acceleration to be up so it is negative.
Example 1: Consider a crate being pulled along a horizontal, frictionless floor. A rope is tied around it and a man pulls on the rope with a force of T. T is the tension in the rope. What happens to the crate?
Safety belts Any passengers in the car will also be decelerated to rest if they are strapped to the car by seat belts. Being strapped tightly to the car, the passengers share the same state of motion as the car. As the car accelerates, the passengers accelerate with it; as the car decelerates, the passengers decelerate with it; and as the car maintains a constant speed, the passengers maintain a constant speed as well.
A disk and a hoop of the same mass M and radius R roll without slipping across a horizontal floor. Both the disk and the hoop are moving with velocity v when the floor starts to slope upward. Which statement is correct? ( )
The net force is (always!) equal to the mass times the acceleration. This fish is moving along with the elevator. In this diagram we have taken the acceleration to be up so it is positive. Fnet = T - m g = m a T = m g+ m a T = m (g + a)
Newton's Second Law tells us that rate of increase (or decrease) in the speed of something which is moving is proportional to the force acting on it. Imagine that you are riding a bicycle along a perfectly smooth and level road and you decide to stop pedaling. If there is a strong wind pushing against you, you will stop completely in a shorter time than you would if the wind was light.
1. Who was the scientist who gave us the Laws of Motion? Answer: Sir Isaac Newton 2. How many Laws of Motion are there? Answer: three 3. What is another name for the first law of motion? Answer: Law of Inertia 4. Which law explains why we need to wear seat belts? Answer: First Law of Motion
(a) The disc makes it to a greater height than the hoop. (b) The hoop makes it to a greater height than the disk. (c) Both the disk and the hoop make it to the same height.
Answer = 50 newtons
Example 2:
This particular example is stated in terms of weighing a fish in an accelerating elevator. It is also fun to think of weighing yourself in an accelerating elevator. When does an elevator accelerate upwards? When does an elevator accelerate downwards?
Fnet = F = T + n + w Fnet, x=F x=Tx+n x+ w x Fnet,y =Fy=Ty+ ny+ w y
n=w
Newton's Second Law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
(a) The disc makes it to a greater height than the hoop. (b) The hoop makes it to a greater height than the disk. (c) Both the disk and the hoop make it to the same height.
or
FORCE = MASS times ACCELERATION
Kobe's car, which weighs 1,000 kg, is out of gas. Kobe is trying to push the car to a gas station, and he makes the car go 0.05 m/s2. Using Newton's Second Law, you can compute how much force Kobe is applying to the car.
These forces are shown on the "free body diagram" above. We have drawn in all the forces acting on the object. The net force is the vector sum of these forces.
A disk and a hoop of the same mass M and radius R roll without slipping across a horizontal floor. Both the disk and the hoop are moving with velocity v when the floor starts to slope upward. Which statement is correct? ( b )
The forces acting on the fish are shown in the free-body diagram. T is the tension supplied by the scale. This is the value the scale reads. We may call it the apparent weight of the fish. The net force on the fish is Fnet = T - mg