Questions and Answers
When you weigh yourself, how does the support force of the scale acting on you compare with the gravitational force between you and Earth?
The support force has the same magnitude as the gravitational force and acts in the opposite direction.
Does a friction force act on a crate if you push it but not hard enough to make it slide?
True
Where would your weight be greater −− on Earth or on the Moon?
On Earth.
Where would your mass be greater −− on Earth or on the Moon?
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What does ⅀F = 0 mean?
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If you push on a heavy crate to the right and it slides, what is the direction of friction on the crate?
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A freely falling object has a speed of 40 m/s at one instant. Exactly one second later its speed will be?
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After he gets the block to move, what does Dr. Hewitt do to drag the block across the table at a steady rate?
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If Dr. Hewitt applies 3 N of force to keep the block moving at a steady rate, what must be the force of friction, and why?
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You are dragging a block on a surface with friction at a steady speed of 2 m/s and exert a force of 5 N to do so. What is the force of friction? Why?
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What general rule can you conclude about the force needed to keep an object in motion at a steady rate?
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What is the name of the property of objects to maintain their states of motion?
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Rank the net force on the block from greatest to least in the four situations A, B, C, and D.
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Does a friction force act on a crate if you push it but not hard enough to make it slide?
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When you toss a ball upward, by how much does its upward speed decrease each second?
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How can you use the graph of velocity versus time to estimate the acceleration of the ball?
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How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second?
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Why does the distance traveled by the ball in each half second after it is released change in the way in which it does?
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A ball is rolling down an inclined plane. How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second?
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Why does the unit of time appear twice in the definition of acceleration?
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What quantity(ies) is(are) necessary to determine a vector quantity?
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A crate is pushed with a 60 N force and a 20 N force. Find the strength of the net force on the crate when both forces act in the same direction.
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A crate is pushed with a 60 N force and a 20 N force. Find the strength of the net force on the crate when the two forces act in opposite directions.
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Which dominated Galileo's way of extending knowledge −− philosophical discussion or experiment?
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Did Aristotle believe that forces are necessary to keep moving objects moving?
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How does the direction of a friction force compare with the direction of motion of a sliding object?
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What equation shows the relationship among velocity, time, and acceleration?
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Which has the greater density −− 1 kg of water or 10 kg of water?
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Why do we say that velocity is a vector and speed is not a vector?
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What were Aristotle's two main classifications of motion? (Check the two options that apply)
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One kg weighs 10 N on Earth. Would it weigh more or less on the Moon?
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Which depends on gravity −− weight or mass?
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How much rope tension holds a 24 N bag of apples at rest?
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From greatest to least, rank them by how much they resist being set in motion.
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From greatest to least, rank them by the support (normal) force the table exerts on them.
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Find the speed of fall at t = 6 s.
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Find the distance of fall at t = 6 s.
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Find the speed of fall at t = 7 s.
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Find the distance of fall at t = 7 s.
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Find the speed of fall at t = 8 s.
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Find the distance of fall at t = 8 s.
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Find the speed of fall at t = 9 s.
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Find the distance of fall at t = 9 s.
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Find the speed of fall at t = 10 s.
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Find the distance of fall at t = 10 s.
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Does the speedometer on a vehicle show the average speed or the instantaneous speed?
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What equation shows the relationship among speed, distance, and time?
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Neglecting air resistance, when you toss a rock upward, by about how much does its upward speed decrease each second?
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Study Notes
Forces and Motion
- Support force equals gravitational force in magnitude but acts in the opposite direction.
- A friction force acts on a non-sliding crate to maintain ∑F = 0, opposing the applied push.
- Weight is greater on Earth due to stronger gravity; mass remains constant regardless of location.
- The net force on an object can be zero if opposing forces balance each other out.
Friction and Motion
- Friction acts opposite to the direction of motion; if a crate slides to the right, friction acts to the left.
- To move an object at a steady rate, the applied force must equal the force of friction, resulting in no net force.
- Inertia is the property that allows objects to maintain their state of motion.
Acceleration and Velocity
- A freely falling object increases speed by 10 m/s every second due to gravitational acceleration.
- The distance traveled by falling objects increases over time due to constant acceleration from gravity.
- The slope of a velocity versus time graph indicates acceleration; velocity involves both magnitude and direction.
Forces and Weight
- Weight depends on gravity and thus is less on the Moon than on Earth, where 1 kg weighs about 10 N.
- Tension in a rope holding an object at rest equals the weight of the object.
Motion Classifications
- Galileo favored experiments over philosophical discussions to expand knowledge; Aristotle classified motion as natural or violent.
- Aristotle believed that continuous applied forces are necessary to keep objects in motion.
Measuring Motion
- Speed of a falling object increases by 10 m/s each second; at t = 6 s, the speed is 60 m/s, and distance fallen is 180 m.
- By the 10th second, speed reaches 100 m/s, and distance fallen totals 500 m.
- A speedometer indicates instantaneous speed rather than average speed.
Basic Physics Equations
- Acceleration can be calculated using the equation: Acceleration = change in velocity / time interval.
- Speed is defined by the equation: Speed = distance covered / travel time.
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Description
This quiz covers the fundamental concepts of forces, motion, and friction. It addresses how these forces interact, the role of gravity, and the impact of mass and acceleration on movement. Test your understanding of these critical physics principles.
