Physics Forces Quiz 01

A rocket in space can travel without engine power at constant speed in the same direction. This condition is best explained by the concept of:

• frames of reference.

• gravity.

• acceleration.

• inertia.

Answer explanation

The rocket's ability to travel at constant speed without engine power is due to inertia, which is the tendency of an object to maintain its state of motion unless acted upon by an external force.

If the mass of a moving object is doubled, its inertia would be:

• halved.

• the same.

• doubled.

• four times greater.

Answer explanation

Inertia is directly proportional to mass. If the mass of an object is doubled, its inertia also doubles. Therefore, the correct answer is that the inertia would be doubled.

Tags

NGSS.HS-PS2-1

A coin is resting on a piece of cardboard on a beaker as shown in the diagram. When the cardboard is rapidly removed, the coin falls into the beaker. The two properties of the coin that best explain its fall are its weight and its:

• inertia.

• volume.

• temperature.

• shape.

Answer explanation

The coin's fall is primarily due to its weight, which pulls it down, and its inertia, which is the tendency to maintain its state of motion. When the cardboard is removed, the coin's inertia causes it to continue moving downward into the beaker.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

If there is no net force acting on a moving object, the object will:

• change its direction of motion.

• accelerate.

• continue with constant speed in a straight line.

• slow down and stop.

Answer explanation

According to Newton's first law, an object with no net force acting on it will maintain its state of motion, which means it will continue with constant speed in a straight line.

Which person has the greatest inertia?

• A 90-kg man walking at 2 m/s

• A 110-kg wrestler resting on a mat

• A 50-kg girl sprinting at 9 m/s

• A 70-kg long-distance runner traveling at 5 m/s

Answer explanation

Inertia is directly related to mass. The 110-kg wrestler has the greatest mass, thus the greatest inertia, even though he is resting. The other options have lower mass, affecting their inertia.

Tags

NGSS.MS-PS2-2

A box is sliding along a frictionless, horizontal surface. Which of the following describes the motion of the box as it continues to slide along the surface?

• The box will slow down as it uses up its speed.

• The box will continue to slide with constant speed only if it is rolling downhill.

• The box will slow down as it runs out of the force of motion.

• The box will continue to slide with constant speed.

Answer explanation

The box will continue to slide with constant speed because there are no forces acting on it to change its motion, as it is on a frictionless surface. According to Newton's first law, an object in motion stays in motion.

Which object has the most inertia?

• a 10-kg tricycle at rest

• a 5-kg bowling ball traveling at 3 m/s

• a 0.001-kg bumblebee traveling at 2 m/s

• a 0.1-kg baseball traveling at 20 m/s

Answer explanation

Inertia depends on mass; the more mass an object has, the more inertia it possesses. The 10-kg tricycle at rest has the greatest mass compared to the other options, making it the object with the most inertia.

Tags

NGSS.MS-PS2-2

John observed his little sister pushing on a block. Because he was studying forces at school, John wondered about the motion of the block in the situation in which all of the forces on the block were balanced. Choose the answer the best describes what the block will be doing.

• The block would have to be slowing down.

• The block would have to be at rest.

• The block could be going at any constant speed, including being at rest.

• The block would have to be moving at a constant speed.

Answer explanation

When all forces on the block are balanced, it can either be at rest or moving at a constant speed. Thus, the correct choice is that the block could be going at any constant speed, including being at rest.

Jim puts a block on a very slippery table and gives it a shove. After he lets go, the block slides across the table with an almost constant speed.

Which statement best describes the horizontal forces on the block as it slides across the table to the right?

• A constant force of motion keeps the block moving to the right.

• The force to the right is greater than the frictional force to the left.

• The force to the right is zero; the frictional force to the left is very small.

• A force of motion to the right is proportional to the speed.

Answer explanation

As the block slides with almost constant speed, the net horizontal force is zero. The frictional force is very small, allowing the block to maintain its motion without any significant force acting to the right.

Tags

NGSS.MS-PS2-2

John tried to move a table sideways, but could not make it move even though he pushed on it sideways. Why didn't the table move?

• John's push is not large enough to overcome the inertia of the table.

• If the table is not moving, the force by John must be zero.

• The frictional force on the table is larger than John's push on the table.

• The frictional force on the table is equal to John's push on the table.

• John's push is not large enough to overcome the gravitational force on the table.

Answer explanation

The table did not move because the frictional force opposing John's push was equal to the force he applied. This balance of forces means that the table remains stationary.

Tags

NGSS.MS-PS2-2