Friction

Which of the following is a situation where we would want to increase friction to prevent objects from sliding?

• Walking on an icy sidewalk

• Sliding down a water slide

• Rolling a ball on a smooth floor

• Skating on ice

Answer explanation

Walking on an icy sidewalk requires increased friction to prevent slipping. The other options involve scenarios where less friction is desirable for smooth movement, making them unsuitable for this context.

Which of the following is a situation where we would want to decrease friction to allow objects to slide past one another more easily?

• Sliding furniture across the floor

• Braking a car to stop quickly

• Walking on a rough surface

• Climbing a hill

Answer explanation

Decreasing friction is beneficial when sliding furniture across the floor, as it allows the furniture to move more easily. In contrast, high friction is needed for braking a car, walking, or climbing.

Lisa is going rock-climbing. In which of the following areas would she want to increase friction, and why?

• On her hands and shoes, to prevent slipping

• On her clothes, to look stylish

• On the rocks, to make them smoother

• On her helmet, to make it heavier

Answer explanation

Lisa should increase friction on her hands and shoes to prevent slipping while climbing. This is crucial for maintaining grip on the rocks and ensuring her safety during the climb.

Sam is going snow-skiing. In which areas of his gear would he want to decrease friction, and why?

• On the bottom of his skis, to help him glide smoothly over the snow

• On his gloves, to help him grip the ski poles better

• On his jacket, to keep him warm

• On his helmet, to protect his head

Answer explanation

Sam should decrease friction on the bottom of his skis to enhance glide over the snow, allowing for smoother and faster movement. Reducing friction here is crucial for effective skiing.

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NGSS.MS-PS2-1

NGSS.MS-PS2-2

Adding wheels to an object generally increases or decreases the friction of the object because:

• It increases friction because more of the object touches the surface.

• It decreases friction because less of the object touches the surface.

• It increases friction because wheels are rougher than the object.

• It does not affect friction at all.

Answer explanation

Adding wheels decreases friction because they reduce the contact area with the surface. Less contact means less friction, allowing the object to move more easily.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

What is inertia?

• Inertia is the tendency of objects to resist changing their motion, meaning moving objects keep moving and still objects stay still unless acted upon by an outside force.

• Inertia is the force that causes objects to move faster when pushed.

• Inertia is the energy stored in moving objects.

• Inertia is the ability of objects to change their shape easily.

Answer explanation

The correct choice defines inertia accurately as the tendency of objects to resist changes in their motion, highlighting that moving objects continue moving and still objects remain still unless influenced by an external force.

According to Isaac Newton's first law of motion, what will happen to a moving object if nothing forces it to change?

• The moving object will keep moving forever.

• The moving object will stop immediately.

• The moving object will slow down and stop.

• The moving object will change direction.

Answer explanation

According to Newton's first law of motion, an object in motion will remain in motion at a constant velocity unless acted upon by an external force. Therefore, the correct answer is that the moving object will keep moving forever.

Inertia is the reason why your ball rolls and rolls until friction finally forces it to stop.

• True

• False

Answer explanation

True. Inertia is the property of matter that causes an object to remain in motion unless acted upon by an external force, like friction. Thus, the ball continues to roll until friction stops it.

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NGSS.HS-PS2-1

What does the diagram illustrate about inertia?

• The diagram illustrates that when the bike stops suddenly, the person continues moving forward due to inertia.

• The diagram illustrates that the person and the bike stop at the same time due to inertia.

• The diagram illustrates that inertia causes the bike to move faster when stopping.

• The diagram illustrates that inertia makes the person move backward when the bike stops.

Answer explanation

The correct choice explains that when the bike stops suddenly, inertia causes the person to continue moving forward, illustrating the concept of inertia effectively.

How is the amount of force required to interrupt an object's inertia related to the object's mass or size?

• The amount of force required is directly related to the object's mass or size. Larger objects require more force to change their motion than smaller objects.

• The amount of force required is inversely related to the object's mass or size. Larger objects require less force to change their motion than smaller objects.

• The amount of force required is not related to the object's mass or size at all.

• The amount of force required is only related to the object's speed, not its mass or size.

Answer explanation

The amount of force required to change an object's motion is directly related to its mass. According to Newton's second law, larger objects have greater inertia, thus requiring more force to alter their state of motion.

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NGSS.MS-PS2-2