| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
How much tension is there in the wire when the body is moving?
Answer: 1,8 N
Exercise 3.7 D
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Determine the mass of the yellow metal weight.
Answer: 77 g
Exercise 3.7 E
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
What is the average force exerted to the puck by the stick?
Tip: The impulse caused by the force is equal to the change in impulse-momentum.
Answer: 160 N
Exercise 3.7 F
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
What is the average force exerted to the bandy ball by the stick?
Tip: The impulse caused by force is equal to the change in impulse-momentum.
Answer: 190 N
Exercise 3.7 G
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
What is the average force exerted to the tennis ball by the racket?
Tip: The impulse caused by force is equal to the change in impulse-momentum.
Answer: 440 N
Exercise 3.7 H
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Define the average force on the ball during the acceleration. a) By means of the basic law mechanics: ∑ F̅ = ma̅. b) Through the power impulse: F∆t = m∆v
Answer: 0,08 N
Exercise 3.8 A
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Compare the amount of work done when lifting or pulling a piece on a sloping level to height h.
Answer: It is noticed that the work on the sloping level to height h is slightly larger than the lifting work at the same height. The reason is the friction between the substrate and the body. In this work, the friction force is low (the piece is pulled by wheels) but it is noticeable. If there was no friction force, the work would be the same. The table clearly shows that doing the same work with less force will cause the distance to extend.
Exercise 3.8 B
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Determine the work done by the force.
Answer: $1{,}3 \ J$
Exercise 3.8 C
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Specify the amount of power to the move of the body.
Answer: $0{,}15 \ W$
Exercise 3.9 A
| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Specify the coefficient of kinetic friction between the body and the surface.
Answer: 0,11
