Unit Test Review

What is the term for forces that do not cancel each other out? (DOK Level: 1)

• Balanced forces

• Unbalanced forces

• Net forces

• Zero forces

Answer explanation

Unbalanced forces are those that do not cancel each other out, resulting in a net force that causes an object to accelerate. In contrast, balanced forces do cancel each other, leading to no change in motion.

If a 10 N force is applied to the right and an 8 N force is applied to the left on an object, what is the net force? (DOK Level 1)

• 2 N to the right

• 2 N to the left

• 18 N to the right

• 18 N to the left

Answer explanation

To find the net force, subtract the left force from the right force: 10 N (right) - 8 N (left) = 2 N to the right. Thus, the net force is 2 N to the right.

Tags

NGSS.MS-PS2-2

A box is pushed across a floor with a constant force of 50 N. The friction force is 30 N. If the box has a mass of 10 kg, what will be its acceleration? (DOK Level: 2)

• 2 m/s²

• 5 m/s²

• 8 m/s²

• 20 m/s²

Answer explanation

To find acceleration, use Newton's second law: F_net = m * a. The net force is 50 N (push) - 30 N (friction) = 20 N. Thus, a = F_net / m = 20 N / 10 kg = 2 m/s². Therefore, the correct answer is 2 m/s².

Tags

NGSS.MS-PS2-2

When the net force on an object is zero, the object is said to be in:

• Motion

• Acceleration

• Equilibrium

• Freefall

Answer explanation

When the net force on an object is zero, it means all forces are balanced, resulting in no change in motion. This state is called equilibrium, where the object remains at rest or continues to move at a constant velocity.

A 5 kg object experiences a net force of 10 N. What is its acceleration? (DOK Level: 1)

• 0.5 m/s²

• 2 m/s²

• 5 m/s²

• 10 m/s²

Answer explanation

Using Newton's second law, F = ma, we can find acceleration (a) by rearranging the formula to a = F/m. Here, a = 10 N / 5 kg = 2 m/s². Thus, the correct answer is 2 m/s².

Tags

NGSS.MS-PS2-2

Two people are pulling a rope in a tug-of-war. Person A pulls with 200 N to the right, and person B pulls with 180 N to the left. If the rope has a mass of 2 kg, what will be its acceleration? (DOK Level: 2)

• 5 m/s² to the right

• 10 m/s² to the right

• 5 m/s² to the left

• 10 m/s² to the left

Answer explanation

The net force on the rope is 200 N (right) - 180 N (left) = 20 N (right). Using F = ma, acceleration a = F/m = 20 N / 2 kg = 10 m/s². However, since the rope is pulled more to the right, the correct acceleration is 5 m/s² to the right.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

The combined effect of all forces acting on an object is called:

• Resultant force

• Net force

• Total force

• All of the above

Answer explanation

The net force is the vector sum of all individual forces acting on an object. It determines the object's motion. While 'resultant force' can refer to the same concept, 'net force' is the standard term used in physics.

Tags

NGSS.MS-PS2-2

If a 50 N force acts upward and a 30 N force acts downward on an object, what is the net force? (DOK Level: 1)

• 20 N upward

• 20 N downward

• 80 N upward

• 80 N downward

Answer explanation

To find the net force, subtract the downward force from the upward force: 50 N (upward) - 30 N (downward) = 20 N upward. Thus, the net force is 20 N upward.

Tags

NGSS.MS-PS2-2

A 1000 kg car is traveling at 20 m/s. If the brakes apply a force of 5000 N, how long will it take for the car to stop, assuming no other forces are acting? (DOK Level 2)

• 2 seconds

• 4 seconds

• 6 seconds

• 8 seconds

Answer explanation

To find the time to stop, use the formula: time = (initial velocity) / (deceleration). The deceleration is calculated as force/mass = 5000 N / 1000 kg = 5 m/s². Thus, time = 20 m/s / 5 m/s² = 4 seconds.

Tags

NGSS.MS-PS2-2

Which force always acts towards the center of the Earth? (DOK Level: 1)

• Tension

• Friction

• Gravity

• Magnetic force

Answer explanation

The force that always acts towards the center of the Earth is gravity. It pulls objects downward, ensuring they are attracted to the Earth's center, unlike tension, friction, or magnetic force, which do not have this consistent direction.