FRICTION, -i, cf. 1. The force that prevents the movement of one body on the surface of another (special). Friction coefficient. Kinematic t. (between moving bodies). T. rest (between motionless bodies). 2. The movement of an object along the surface of another object that is in close contact with it. Parts worn out from friction. 3., pl. h. Hostile clashes, disputes that interfere with the course of business. Friction between colleagues. Friction with the boss.

The friction force is the force that arises when one body moves along the surface of another, applied to the moving body and directed against the movement. The friction force is the force that arises when one body moves along the surface of another, applied to the moving body and directed against the movement.

In the winter twilight, Sasha loved the fairy tales of her nanny. In the morning, Sasha sat in the sleigh, flew like an arrow, Full of happiness, from the icy mountain. Though it is sometimes heavy in her burden, The cart is light on the move; A dashing coachman, gray time, Lucky, will not get off the irradiation. A cat for a bug, a bug for a granddaughter, a granddaughter for a grandmother, a grandmother for a grandfather, a grandfather for a turnip, they pull - they pull, they cannot pull it out.

about board. The impact duration is 0.01 s.
2) A hammer of mass 100 kg falls from a height of 1.5 m onto a package. Determines the average force of the impact of the hammer on the anvil, if it lasts 0.05 seconds
3) A ball of mass 50 g falls freely without initial speed from a height of 2 m to the floor and jumps to a height of 1 m. Determine the average force of the ball hitting the floor. The impact duration is 0.02 s.
4) What speed does a rocket with a mass of 1000 g acquire, excluding fuel, if combustion products with a mass of 200 g fly out of it at a speed of 900 m / s.
5) a body with a mass of 200 g moving horizontally at a speed of 10 m / s as a result of a force impulse changed the direction of movement by an angle of 60 degrees. Determine the magnitude and direction of the force impulse if the modulus of the body's velocity remained the same.

People explain only normally, it is very necessary!!

1) Train compartment 2) Book lying on the table 3) Platforms 4) All of the above

2. The speed of the river is 2m/s, the speed of the motor boat is 6m/s. How long does it take a fisherman to climb 60 meters upstream?

3. A freight train has left the station, its speed is 54 km/h. An hour later, an express train left in the same direction, its speed was 72 km/h. While the trains...
1) Moving away at a speed of 18 km/h 2) Approaching at a speed of 18 km/h
3) Do not change the distance from each other 3) Can approach and move away at a speed of 126 km / h

4. Along the course of the river, the boat travels a distance of 35 km in 2.5 hours. How long will it take the boat to overcome this distance against the current of the river, if the speed of the river is 2 km/h

5. Two trains are moving towards each other with speeds of 90 km/h and 54 km/h. A passenger on the second train notices that the first train passes him within 15 seconds. What is the length of the first train?

6. A fisherman crosses a river in a boat. The figure (I attached it) shows the direction of the boat and the direction of the river. How will the total displacement vector be directed?
1) To the south 2) To the northeast 3) To the northwest 4) To the southwest

7. Using the drawing of the previous problem, calculate the module of the total displacement, if it is known that the width of the river is 30 m, the speed of the boat is 8 m/s. A fisherman on a boat crossed the river in 5 seconds. 1) 24 m 2) 50 m 3) 25 m 3) 40 m

8. The speed of the ship relative to the shore down the river is 28 km / h, and up - 18 km / h. What is the speed of the river?

9. Using the condition of the previous problem, calculate the speed of the ship and indicate the correct answer 1) 46 km/h 2) 23 km/h 3) 19 km/h 4) 12 km/h

component of its momentum and the potential energy of the stone in the gravitational field?

Grade 7 Option 1

1. Strength is a reason ...

1) body movements

2) weight gain

3) changes in body speed

3) on the size of the body

3) the force of gravity of the earth

3) when deformed

3) will be halved

Grade 7 Option 1

1. Strength is a reason ...

1) body movements

2) weight gain

3) changes in body speed

2. According to the International Agreement, the unit of force is accepted ...

1) kilogram 2) Newton 3) meter

3. What does gravity depend on?

1) from body weight 2) from body density

3) on the size of the body

4. What force changes the direction of motion of a stone thrown horizontally?

1) air elasticity force 2) stone elasticity force

3) the force of gravity of the earth

5. When does the force of elasticity arise?

1) when the body moves 2) when the body stops

3) when deformed

6. How will the elastic force change if the elongation of the spring is doubled?

1) stay the same 2) double

3) will be halved

Grade 7 Option 1

1. Strength is a reason ...

1) body movements

2) weight gain

3) changes in body speed

2. According to the International Agreement, the unit of force is accepted ...

1) kilogram 2) Newton 3) meter

3. What does gravity depend on?

1) from body weight 2) from body density

3) on the size of the body

4. What force changes the direction of motion of a stone thrown horizontally?

1) air elasticity force 2) stone elasticity force

3) the force of gravity of the earth

5. When does the force of elasticity arise?

1) when the body moves 2) when the body stops

3) when deformed

6. How will the elastic force change if the elongation of the spring is doubled?

1) stay the same 2) double

3) will be halved

Grade 7 Option 2

1) F = k ∆ l 2) m = V 3) s = vt

3) for all types of deformation

Grade 7 Option 2

1. Gravity is the force with which ...

1) the body, due to attraction to the Earth, acts on a support or suspension 2) the body is attracted to the Earth

3) the body attracts other bodies to itself

2. The stone falls to the Earth due to the fact that it is affected by ...

1) body weight 2) elastic force 3) gravity

3. What determines the action of force on the body?

1) from the force module and its direction 2) from the force module

3) on the modulus of force, its direction and point of application

4. Which wagons attract each other with greater force: empty or loaded, if the distance between the wagons is equal?

1) empty 2) loaded 3) gravity does not depend on mass

5. Which of the following formulas corresponds to Hooke's law?

1) F = k ∆ l 2) m = V 3) s = vt

6. Under what deformations is Hooke's law valid7

1) in compression and tension 2) in bending and torsion

3) for all types of deformation

4) for all deformations, if they are elastic deformations

Grade 7 Option 2

1. Gravity is the force with which ...

1) the body, due to attraction to the Earth, acts on a support or suspension 2) the body is attracted to the Earth

3) the body attracts other bodies to itself

2. The stone falls to the Earth due to the fact that it is affected by ...

1) body weight 2) elastic force 3) gravity

3. What determines the action of force on the body?

1) from the force module and its direction 2) from the force module

3) on the modulus of force, its direction and point of application

4. Which wagons attract each other with greater force: empty or loaded, if the distance between the wagons is equal?

1) empty 2) loaded 3) gravity does not depend on mass

5. Which of the following formulas corresponds to Hooke's law?

1) F = k ∆ l 2) m = V 3) s = vt

6. Under what deformations is Hooke's law valid7

1) in compression and tension 2) in bending and torsion

3) for all types of deformation

4) for all deformations, if they are elastic deformations