# Lesson Worksheet: Newton’s First Law of Motion Physics • 9th Grade

In this worksheet, we will practice analyzing systems of forces that produce no net acceleration.

Q1:

Which of the following statements most correctly describes Newton's first law of motion?

• AAn object will change direction if a net force acts on the object.
• BAn object will not change its velocity unless a net force acts on the object.
• CAn object will move until a net force acts on the object.
• DAn object will not move unless a net force acts on the object.

Q2:

A book at rest on a table has a weight of 8 N.

At what rate is the book accelerating?

What is the net force acting on the book?

What magnitude force does the table apply to the book?

Q3:

A ship with a weight of 7,000 N has both a motor and sails. The ship moves at a constant speed across the surface of the sea. The motor provides a force of 8,500 N and the drag from the water around the ship produces a force of 6,000 N. The wind is blowing in the opposite direction to the motion of the ship, so the sails provide a drag force on the ship.

What is the force on the ship from the wind pushing on its sails?

• A6,000 N
• B2,500 N
• C N
• D8,500 N
• E N

How many newtons of force does the water underneath the ship apply upward on the ship’s hull?

• A6,000 N
• B1,000 N
• C7,000 N
• D2,500 N
• E8,500 N

Q4:

A satellite orbits Earth at a constant speed, traveling in a circle around Earth. Which of the following diagrams correctly shows the forces acting on the satellite, where the forces are shown by black arrows? The satellite is completely outside Earth’s atmosphere and has no engine. • A(a)
• B(b)
• C(c)
• D(e)
• E(d)

Q5:

Fill in the blanks: An object that is initially at rest and has two forces acting on it will remain at rest if the forces acting on it have and act in .

• Adifferent magnitudes, the same direction
• Bdifferent magnitudes, opposite directions
• Cthe same magnitude, the same direction
• Dthe same magnitude, opposite directions

Q6:

The graph shows the velocities of three objects during a time interval. Which of the objects has no net force acting on it during the time interval? • AII
• BIII
• CI

Q7:

A missile is propelled by the thrust from its engine, as shown in the diagram. The missile moves horizontally and at a constant speed, not changing its height above the ground. Any vertical motion of the air around the missile has negligible effect on it. Which of the following forces has a magnitude equal to the vertical component of the thrust force?

1. The weight of the missile
2. The drag on the missile
3. The lift on the missile
4. The thrust on the missile
• Bc
• Cb
• Da

Which of the following forces has a magnitude equal to the horizontal component of the thrust force?

1. The weight of the missile
2. The drag on the missile
3. The lift on the missile
4. The thrust on the missile
• Aa
• Bb
• Cd
• Dc

Q8:

The net force on an object is zero.

Which of the following statements about the object must be true?

• AMultiple forces with magnitudes greater than zero act on the object.
• BThe speed of the object is zero.
• CA single force with a magnitude greater than zero acts on the object.
• DThe speed of the object is constant.

Which of the following statements about the object must be false?

• AMultiple forces with magnitudes greater than zero act on the object.
• BThe speed of the object is constant.
• CThe speed of the object is zero.
• DA single force with a magnitude greater than zero acts on the object.

Q9:

An object travels between point A and point B, where the points are separated by a distance of 2 meters. The object travels this distance in a time interval of 3 seconds and is moving at a constant velocity throughout the time interval. Which of the following must be false?

• AThe speed of the object is zero.
• BThe speed of the object is constant.
• CThe magnitude of the net force that acts on the object does not change during the time interval.
• DNo forces act on the object.

Q10:

A bike runs with a uniform velocity of 8 m/s in the direction of the west. The bike’s mass is 92 kg. Find the resultant force acting on the bike.

• A902 N
• B0 N
• C120 N
• D736 N