Exam of Physics and Chemistry, 4th ESO.

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1. On a horizontal surface a box is pulled by a force of 70 N that forms an angle of 10 with the floor. The mass of the box is 45 kg and the coefficient of friction with the floor is 0.13. Calculate:

a) The acceleration the box acquires. (1 point)

b) The space it travels in 7 seconds, if the force is maintained. (0.5 points)

c) The speed the box has after 7 seconds, if the force is maintained. (0.5 points)

2. A box moves with a velocity of 40 m/s on a surface which has a coefficient of friction of 0.1. This box has a mass of 20 kg. What is the force you need to apply if you want the box to stop in 10 seconds? (2 points)

3. The maximum speed an Alvia train can take a radius of 400 m without derailing is 80 km/h. This type of train has a mass of 375 tons. Calculate the centripetal force when it turns with the maximum speed. (1 point)

4. Venus is the second planet from the Sun. It has no natural satellite. It is named after the Roman goddess of love and beauty. Its period (time it takes to turn one revolution around the Sun) is 224.7 Earth days and its orbital speed is 35020 m/s. Calculate the distance between the centers of Venus and the Sun and calculate the angular speed and the centripetal force of this planet. Data: MSun=1.991030 kg. MVenus=4.871024 kg. (2 points)

5. Mercury is the smallest planet in the Solar System and the one closest to the Sun.

a) Calculate the force of attraction between Mercury and the Sun. (1 point)

b) Calculate the acceleration of gravity in Mercury at a height of 25 km. (1 point)

c) Calculate the orbital speed of Mercury around the Sun and its period. (1 point)

MMercury=3.301023 kg; MSun=1.991030 kg; RMercury=2440 km; RSun=696342 km; average distance between the centers of Mercury and the Sun=5.791010 m.

Answers

1. On a horizontal surface a box is pulled by a force of 70 N that forms an angle of 10 with the floor. The mass of the box is 45 kg and the coefficient of friction with the floor is 0.13. Calculate:

a) The acceleration the box acquires. (1 point)

b) The space it travels in 7 seconds, if the force is maintained. (0.5 points)

c) The speed the box has after 7 seconds, if the force is maintained. (0.5 points)

seconds.

a) Fx=Fcos10=70cos10=68.94 NFy=Fsin10=70sin10=12.16 N

Y axis

N+Fy-mg=0 N=mg-Fy=459.8-12.16=428.84 N

X axis

Ffr=N=0.13428.84=55.75 N

Fx-Ffr=ma

b)

c) v=v0+at=0+0.297=2.05 m/s

2. A box moves with a velocity of 40 m/s on a surface which has a coefficient of friction of 0.1. This box has a mass of 20 kg. What is the force you need to apply if you want the box to stop in 10 seconds? (2 points)

3. The maximum speed an Alvia train can take a radius of 400 m without derailing is 80 km/h. This type of train has a mass of 375 tons. Calculate the centripetal force when it turns with the maximum speed. (1 point)

4. Venus is the second planet from the Sun. It has no natural satellite. It is named after the Roman goddess of love and beauty. Its period (time it takes to turn one revolution around the Sun) is 224.7 Earth days and its orbital speed is 35020 m/s. Calculate the distance between the centers of Venus and the Sun and calculate the angular speed and the centripetal force of this planet. Data: MSun=1.991030 kg. MVenus=4.871024 kg. (2 points)

5. Mercury is the smallest planet in the Solar System and the one closest to the Sun.

a) Calculate the force of attraction between Mercury and the Sun. (1 point)

b) Calculate the acceleration of gravity in Mercury at a height of 25 km. (1 point)

c) Calculate the orbital speed of Mercury around the Sun and its period. (1 point)

MMercury=3.301023 kg; MSun=1.991030 kg; RMercury=2440 km; RSun=696342 km; average distance between the centers of Mercury and the Sun=5.791010 m.

a)

b)

c)