Gravity
Why do objects fall at the same rate in a vacuum, regardless of mass?
Because gravity accelerates all objects equally when no other forces (like air resistance) act on them.
Why do astronauts experience almost no friction when moving inside the International Space Station?
Because there is very little gravity to create contact force between their bodies and surfaces, reducing friction.
A cyclist travels 30 km in 1.5 hours. What is their average speed?
20 km/h
Which law explains why you feel a jolt backward when a bus suddenly moves forward?
Newton's first law (inertia)
What is a net force?
The overall force acting on an object after all forces are combined.
What is the relationship between mass and gravitational force?
More massive objects exert a stronger gravitational force.
How does lubrication (like oil or grease) reduce friction between machine parts?
It creates a slippery layer that prevents direct contact between surfaces, lowering resistance.
How does acceleration differ from speed?
Speed is how fast something moves; acceleration is how quickly speed or direction changes.
A 10 kg object accelerates at 3 m/s². What is the net force acting on it?
30 N (F = ma)
What causes an object to start moving if it's at rest?
An unbalanced force.
Why does your weight change on different planets, but your mass stays the same?
Weight depends on the gravitational pull of the planet, while mass is the amount of matter you contain.
Why do tires have more friction on a dry road than on an icy road?
Ice is smoother and provides less resistance, while dry pavement has more texture to grip the tires.
What is the acceleration of an object that goes from 0 m/s to 10 m/s in 2 seconds?
5 m/s²
Why do rockets accelerate more as they burn fuel and get lighter, even if thrust stays the same?
With less mass, the same force produces more acceleration (Newton’s second law).
A 15 N force pulls right and a 10 N force pulls left. What is the net force and direction?
5 N to the right.
If the Earth suddenly doubled in mass but stayed the same size, how would your weight change?
Your weight would double, because gravitational force increases with mass.
Explain why friction is both helpful and harmful in mechanical systems.
Helpful for grip and stopping motion; harmful because it causes wear and energy loss as heat.
What type of graph shows how distance changes over time?
Line graph
A hammer strikes a nail. Explain how Newton’s third law applies to both the hammer and nail.
The hammer exerts force on the nail; the nail pushes back with equal force on the hammer.
Why doesn’t a book on a table fall through it, even though gravity pulls it down?
The table provides an equal and opposite normal force upward.
A satellite orbits Earth at a constant speed. Why doesn’t it fall straight down due to gravity?
Its forward velocity balances the downward pull of gravity, creating orbit.
Two blocks are pushed with equal force on different surfaces. One accelerates more. What can you infer about the frictional forces involved?
The surface where the block accelerates more has less friction.
A car increases its speed from 10 m/s to 30 m/s over 4 seconds. What is its average acceleration?
5 m/s²
A student says heavier objects fall faster in a vacuum because of their mass. Use Newton’s laws to explain why this is incorrect.
The idea that heavier objects fall faster solely due to their mass is incorrect. While heavier objects experience a stronger gravitational force, they also have a greater inertia, meaning they resist changes in motion more. These effects cancel each other out, resulting in all objects falling at the same rate in a vacuum (where air resistance is negligible) due to the constant acceleration of gravity.
Describe how net force, mass, and acceleration are related.
Net force equals mass times acceleration (F = ma); more force means more acceleration, unless mass increases.