Urgent!! Physics problems, help! Physics

Choose D, draw a triangle of force and the diagram will come out, the gravity is unchanged, the force of the rod is in the horizontal direction, so the force of the ob rope becomes smaller first and then becomes larger, and because the force of the rod is horizontal, the moment of the rod to point A is always not zero, the magnitude direction of gravity is unchanged, so the moment of point A is also unchanged, so the moment of ob to point A is also unchanged.

The correct option is d.

Since the light rod AO is fixed by a smooth hinge, the resultant external force on the O end of the rod must be in the direction of OA (the resultant moment is zero), otherwise the rod cannot be stationary.

The force analysis is carried out on the point O, and the rod O end is subjected to the force of two strands of rope, in which the force of the vertical rope on it remains unchanged, and the moment is unchanged; Since the torque of the ob to the rod is opposite to the moment of the vertical rope to the rod, the torque of the ob to the rod is always the same.

The lever is always in equilibrium: clockwise moment = counterclockwise moment. Because the clockwise moment does not change, the counterclockwise moment also does not change

The force becomes smaller first and then becomes greater f=mg cos@

Moment = fl = mg cos@ * lcos@ = mgl The moment is unchanged.

The tensile force of the ob first becomes smaller and then larger, and the torque of the rod remains unchanged, so D is selected

The moment first becomes larger and then smaller, and the force becomes smaller first and then larger.

None of the answers are correct.

b The force is greatest at the top of the heavy object.

Summary. Seek help! Physics

1210 ohms, r u squared divided by p

The second question, p u squared divided by the buried r, the result is 110 * 110 1210 = 10w, current, i is equal to the liquid p u, that is, 1 11a

Summary. Hello, dear, I'm glad to serve you, and please send me a physics question, I see if it will be!

Seek help! Physics

Hello, dear, I'm glad to serve you, and please send me a physics question, I see if it will be!

It can be found from the pv t=constant quantity, v is the volume, which can be replaced by the length of the air column in this problem.

In the first question, t is unchanged, i.e., (p+mg s)h1=(p-mg s)h2, and h2=15cm

In the second question, substituting t=20cm, we can find t=373k, then t=100 degrees Celsius.

0 points... I'd better be busy with something else.

Find the initial velocity at the time of braking.

Because V 2AS, A=5M S, S, so V=12M S=, is a driving violation.

Then ask if there is a security issue.

Reaction time: car forward distance: l=v*t=6m

The braking distance is s=

The total distance traveled is l+s=, so there are no safety issues.

When the car brakes at the maximum acceleration, the car finally stops, and the reverse consideration is that it is a uniform acceleration linear motion with an initial velocity of 0, s=1 2att=, and it can be obtained: t=, and the speed of braking at the beginning is v=at=5*>40km h, which is illegal driving.

Because the object moves horizontally at a constant speed, it is subjected to an equilibrium force. The tensile force f is equal to the frictional force 5n, the distance of horizontal movement is 5m, and the work done by the tensile force f is w=fs=5n*5m=25j

Because it is a uniform motion, the tensile force = friction force = 5n, w = f * s = 5 * 5 = 25j