Test

Which of the following statements about force is correct?

• Force can only make an object move or be at rest.

• There can be no force between non - contacting objects.

• Force is the interaction between objects.

• Force can only change the shape of an object.

Hold a bottle with your hand so that the bottle is stationary in the vertical direction. If you increase the gripping force on the bottle, then the force the bottle receives?

• The gravity increases.

• The friction increases.

• Both the gravity and the friction remain unchanged.

• None of the above statements is correct.

As shown in the figure, use a horizontal force to press a block with a weight of tightly against the vertical wall, and the block is stationary. When the horizontal force is reduced to , the magnitude of the friction force on the block?

• Reduces to half of the original.

• Remains the same as the original.

• Increases to twice the original.

• Cannot be determined.

A 50 - N object is moving in a uniform linear motion under the action of a 12 - N horizontal pulling force. What is the magnitude of the friction force on the object?

• 12N

• 50N

• 38N

• 62N

Which of the following statements about friction is correct?

• Friction always hinders the motion of an object.

• The direction of the sliding friction force is always opposite to the direction of the object's motion.

• The magnitude of the static friction force has nothing to do with the magnitude of the pressure.

• The rolling friction is always smaller than the sliding friction.

An object is under the action of two forces, and the three elements of these two forces are completely the same. Then these two forces?

• Must be balanced forces.

• Must not be balanced forces.

• May be balanced forces.

• Cannot be determined.

An object is only under the action of two forces, and the resultant force of these two forces is zero. Then these two forces must?

• Be equal in magnitude.

• Be in the same direction.

• Act on the same straight line.

• All of the above.

Which of the following statements about elastic force is correct?

• There must be an elastic force between objects in contact.

• An object will generate an elastic force as long as it deforms.

• The direction of the elastic force is always opposite to the direction of the object's elastic deformation.

• The magnitude of the elastic force is only related to the degree of deformation of the object.

An object is moving in a uniform linear motion on a horizontal plane. Now, a force in the same direction as the motion is applied to the object. Under the action of this force, the object will?

• Continue to move in a uniform linear motion.

• The speed will become larger and larger.

• The speed will become smaller and smaller.

• Cannot be determined.

Which of the following statements about the relationship between force and motion is correct?

• When an object is not affected by force, it must remain stationary.

• When an object is under the action of balanced forces, it must move in a uniform linear motion.

• When an object is under the action of unbalanced forces, its motion state must change.

• When there is a force acting on an object, the object must move.