Lesson test: Newton's laws

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Newton's laws

1.[3p]
What does Newton's first law claim that the second law does not already contain?

That frames of reference exist in which a body free of forces moves at constant velocity

Correct

That forces always occur in pairs

The answer is: That frames of reference exist in which a body free of forces moves at constant velocity

That mass is conserved

The answer is: That frames of reference exist in which a body free of forces moves at constant velocity

That acceleration is proportional to force

The answer is: That frames of reference exist in which a body free of forces moves at constant velocity

2.[2p]
A 2.0 kg block on a frictionless surface is pulled by 9.0 N along $x$ and 12.0 N along $y$ . What is the magnitude of its acceleration, in m s⁻²?

CorrectNot quite: 7.5

3.[2p]
A 70 kg person stands on a scale in a lift accelerating upward at 2.0 m s⁻². What does the scale read, in newtons, with $g = 9.81$ m s⁻²?

CorrectNot quite: 827

4.[3p]
A book rests on a table. Which force is the third law partner of the Earth's downward pull on the book?

The book's upward gravitational pull on the Earth

Correct

The table's upward normal force on the book

The answer is: The book's upward gravitational pull on the Earth

The book's downward push on the table

The answer is: The book's upward gravitational pull on the Earth

The weight of the table

The answer is: The book's upward gravitational pull on the Earth

5.[2p]
The two forces in a third law pair can cancel each other in a single body's equation of motion.

True

The answer is: False

False

Correct

6.[2p]
A 4.0 kg rifle fires a 12 g bullet at 850 m s⁻¹. What is the recoil speed of the rifle, in metres per second?

CorrectNot quite: 2.55

7.[3p]
Which of these are true of mass and weight?

Select all that apply

Mass is the same on the Moon as on Earth, while weight is not

Correct

Weight is a force and is measured in newtons

Correct

A scale in a freely falling lift reads zero even though gravity still acts

Correct

Weight is what appears on the right hand side of $\sum \vec{F} = m \vec{a}$

The answer is: Mass is the same on the Moon as on Earth, while weight is not, Weight is a force and is measured in newtons, A scale in a freely falling lift reads zero even though gravity still acts

8.[2p]
Match each historical position to what it claimed about a moving body.

Aristotle
Buridan
Galileo
Newton

motion needs a continuing cause
the thrower gives an impetus that runs out
only a net force changes the momentum
on a frictionless horizontal plane the motion never stops

Show the answer

Aristotle: motion needs a continuing cause Buridan: the thrower gives an impetus that runs out Galileo: on a frictionless horizontal plane the motion never stops Newton: only a net force changes the momentum

9.[3p]
The Earth turns once in 86164 s. What is the centripetal acceleration of a point on the equator, in m s⁻², taking the equatorial radius as $6.378 \times 10^{6}$ m?

CorrectNot quite: 0.0339

1.[3p] What does Newton's first law claim that the second law does not already contain?

2.[2p] A 2.0 kg block on a frictionless surface is pulled by 9.0 N along x and 12.0 N along y. What is the magnitude of its acceleration, in m s⁻²?

3.[2p] A 70 kg person stands on a scale in a lift accelerating upward at 2.0 m s⁻². What does the scale read, in newtons, with g=9.81 m s⁻²?

4.[3p] A book rests on a table. Which force is the third law partner of the Earth's downward pull on the book?

5.[2p] The two forces in a third law pair can cancel each other in a single body's equation of motion.

6.[2p] A 4.0 kg rifle fires a 12 g bullet at 850 m s⁻¹. What is the recoil speed of the rifle, in metres per second?

7.[3p] Which of these are true of mass and weight?

8.[2p] Match each historical position to what it claimed about a moving body.

9.[3p] The Earth turns once in 86164 s. What is the centripetal acceleration of a point on the equator, in m s⁻², taking the equatorial radius as 6.378×106 m?

1.[3p]
What does Newton's first law claim that the second law does not already contain?

2.[2p]
A 2.0 kg block on a frictionless surface is pulled by 9.0 N along $x$ and 12.0 N along $y$ . What is the magnitude of its acceleration, in m s⁻²?

3.[2p]
A 70 kg person stands on a scale in a lift accelerating upward at 2.0 m s⁻². What does the scale read, in newtons, with $g = 9.81$ m s⁻²?

4.[3p]
A book rests on a table. Which force is the third law partner of the Earth's downward pull on the book?

5.[2p]
The two forces in a third law pair can cancel each other in a single body's equation of motion.

6.[2p]
A 4.0 kg rifle fires a 12 g bullet at 850 m s⁻¹. What is the recoil speed of the rifle, in metres per second?

7.[3p]
Which of these are true of mass and weight?

8.[2p]
Match each historical position to what it claimed about a moving body.

9.[3p]
The Earth turns once in 86164 s. What is the centripetal acceleration of a point on the equator, in m s⁻², taking the equatorial radius as $6.378 \times 10^{6}$ m?