Friction
This is the force that opposes motion between two surfaces in contact.
Friction
Velocity tells both how fast an object is moving and this other piece of information.
Direction.
Speed is the rate of change of this quantity (name the quantity).
Distance (or how far an object travels).
Newton's discovery of the force that pulls things toward its center.
Gravity
What is the third planet from the sun?
Earth
Name the type of friction that acts on an object moving through air.
Air resistance
An object moves 30 meters to the east in 10 seconds. What is its average velocity? Provide the answer and show the short calculation
30 m east10 s=3 m/s east10 s30 m east=3 m/s east.
A bicyclist travels 12 kilometers in 0.5 hours. What is the bicyclist’s average speed?
Average speed = distance / time = 12 km0.5 h=24 km/h0.5 h12 km=24 km/h.
The unit of measurement for force
Newtons (N)
What is the largest land animal in the world?
An elephant
A heavy box requires more force to start moving than to keep moving because of this change in friction. Is static friction greater than kinetic friction, or is kinetic greater than static?
Static friction is greater than kinetic friction. Static friction resists the start of motion and typically has a higher maximum value.
A runner moves around a circular track at a constant speed. Is the runner’s velocity constant? Explain why or why not
No. Even though speed is constant, direction is continuously changing on a circular track, so velocity (which includes direction) is not constant.
Explain the difference between instantaneous speed and average speed.
150 km÷3 h=50 km/h
This planet spins backwards.
Venus
Describe one real-world way to reduce friction between two solid surfaces and explain why it works.
Example: Use lubrication (oil) to reduce friction; lubrication creates a thin layer that prevents direct surface-to-surface contact, lowering resistance. Other acceptable answers: use wheels/ball bearings, make surfaces smoother.
A car changes from 20 m/s east to 10 m/s west in 5 seconds. Calculate the average acceleration. Provide the calculation with each numerical expression wrapped in ...... and include units.
Change in velocity = final − initial = (−10 m/s)−(20 m/s)=−30 m/s(−10 m/s)−(20 m/s)=−30 m/s (using east as positive and west negative). Average acceleration = ΔvΔt=−30 m/s5 s=−6 m/s2ΔtΔv=5 s−30 m/s=−6 m/s2
A runner completes a 400-meter lap in 5050 seconds. What is the runner’s average speed in meters per second (m/s)?
The human body has __________ bones.
206 bones
A block slides across a table and slows to a stop because of friction. List the three factors that affect the amount of friction between the block and the table.
Factors: the normal force (related to weight), the types of surfaces in contact (material/roughness), and whether there is lubrication or contaminants (or contact area in some practical contexts). Teacher note: emphasize normal force and surface properties.
Explain the difference between instantaneous velocity and average velocity. Give an example of how you might measure each for a bicyclist during a race.
Instantaneous velocity is the velocity at a specific moment (e.g., using a speedometer/velocity sensor at one instant); average velocity is total displacement divided by total time over an interval (e.g., measure displacement from start to finish and divide by total time).
A bicyclist travels at a constant speed of 6 m/s6 m/s for 1515 minutes. How far does the bicyclist travel in meters?
This part of your body feels no pain.
Brain