# III.4. Recapitulative exercises - Movement and Rest.

🔐 **Recapitulative exercises - Movement and Rest.**

**1. Determine whether the following statements are true (A) or false (F):**

a) A house is at rest relative to the sun.

b) The bus driver is at rest in front of the passengers in the seats.

c) An airplane is in a state of motion relative to the ground.

d) The average speed is the arithmetic mean of the momentary velocities of the mobile.

e) A body is in accelerated rectilinear motion.

f) A mobile has a rotational motion when its trajectory is a circle.

g) In uniform rectilinear motion the mobile travels equal distances in equal time intervals.

h) The graph of uniform rectilinear motion is a straight line.

i) When a body starts it has a slow motion.

j) When a body stops it has an accelerated movement.

**2. Which of the following mobiles has the highest average speed: the first mobile that traveled a distance of 600 hm in 0,3 h or the second mobile that traveled a distance of 50 km in 50 min?**

**3. Transform the following speeds into SI:**

a) v = 5400 dam/h

b) v = 300 dm/min

**4. Transform the following accelerations into SI:**

a) a = 240 cm/min^{2}

b) a = 7800 km/h^{2}

**5. Look carefully at the following graph:**

a) What kind of movement does the mobile have? Why ?

b) Fill in the table with the data of the mobile movement.

c) Determine on the graph the time at position x = 125 km.

d) Determine on the graph the position at t = 0.75 h.

e) Calculate the average speed of the mobile.

f) Write the law of motion of this mobile.

**6. The following table gives the data of the movement of two mobiles M _{1} și M_{2}.**

a) Determine the positions of the mobile M_{2}, knowing the law of motion:

x_{M2} = 20 + 2 ∙ t

b) Make the graphs of the motion of the two mobiles. Standards: 1 cm: 40 hm, 1 cm: 10 min.

c) What is the position of the two mobiles at t = 30 min?

d) Determine the average speeds of the two mobiles.

e) Write the law of motion for the mobile M_{1}.

**7. What is the acceleration of a Formula 1 car that reaches a speed of 100 km / h in 2 s at start-up?**