Warm up.
SPEED. GRAPHS. MOTION. AHH.
FORCES
WORD PROBLEMS
An apple from a tree...
100
Why does a car going around a curve at a constant speed of 35 mph not have a constant velocity?
Velocity is speed with direction. The car is changing direction by going around a curve, and thus does not have a constant velocity.
100
The graph represents the motion of two cars, A and B. During the first 5 seconds, which car is moving faster? How do you know?
Car B is moving faster because the slope of its line is steeper.
100
The diagram represents an object moving to the right with a constant velocity. What is the value of force F?
What is between 1N and 6N?
100
When the starter's gun is fired, a sprinter takes 37.0 seconds to run 350 meters. Calculate the average speed of the runner. For full credit, you must write a proper equation (show the formula), show your work with units, and give the answer with units.
speed = distance / time 350 m / 37.0 s = 9.459 m/s
100
If you were to arrange Newton's 2nd Law into a formula relating force, mass, and acceleration, what would that formula be?
Mass = force/acceleration OR Acceleration = force/mass
200
TRUE OR FALSE: On a distance vs. time graph, constant speed is indicated by a straight, sloped line.
What is true? We may never know.
200
The distance vs. time graph represents the position of an object moving in a straight line. Calculate the speed of the object from 2 seconds to 4 seconds.
Speed = slope of distance vs. time graph slope = 30m - 10m / 4.0 s - 20s = 20m / 2s = 10 m/s
200
Friction can be useful. List four ways and give a brief explanation for each.
Friction between tires and roads keeps car accidents from happening left and right. Friction between shoes, like soccer cleats, and the ground prevents a player from slipping while accelerating. Friction between nails and wood in construction keeps the nail from slipping out, which is good because I bet you like a roof over your head. Friction between the brake pads and brake discs of a car allows a decelerating force to be applied to the car, so that we don't create reenactments of Newton's 1st Law left and right.
200
Toby, a truck driver, claims that if he were able to drive his twelve ton truck on the moon, it would require less force to bring it to a stop than on earth. Is Toby right or wrong? Use the words weight, mass, and inertia to explain your answer.
Toby is wrong. Inertia is a property of matter that resists a change in motion of an object. The greater the mass, the greater the inertia. Even though the truck has a smaller weight on the moon, its mass is the same, and thus it would require the same force to bring it to a stop.
200
For any two objects, these two variables determine the strength of the gravitational force of attraction between two objects.
What is the mass of an object and the distance between the two objects.
300
Why do you not notice the force of gravity between you and a friend?
The force of gravity depends on distance between two objects, but also MASS. At least one of the objects must have a huge mass, at least the size of the Earth or Moon, in order for the force to be noticeable.
300
The graph represents the motion of two cars, A and B, moving on a straight track. Calculate the distance car B moves in 50 seconds.
Distance = 30 m/s x 50 s = 1500 m
300
Zane has a mass of 48 kilograms. Calculate his weight in newtons.
W = mg (48 kg)(9.8 m/s^2) = 470.4 N
300
Maria rolls a ball down her driveway. If the ball leaves her hand traveling at 3 meters per second and is traveling at 12 meters per second four seconds later, calculate the acceleration of the ball.
2.25 m/s^2
300
State them. All THREE of them. You know what I mean.
1: An object at rest will stay at rest and an object in motion will remain in motion unless acted upon by some net force. 2: Force causes acceleration, and mass resists it. 3: For every action, there is an equal and opposite reaction.
400
You drop an elephant and a feather in a vacuum. Which hits the ground first? Explain why.
Both fall at the same time in a vacuum, because the strength of gravity acting upon an object is the same for all objects, and there would be no air resistance.
400
Explain the difference between speed, velocity, and acceleration.
Speed is the distance an object travels in a given amount of time. Velocity is speed with direction. Acceleration is a rate: how much an object's speed is changing over time.
400
What is the difference between static friction and sliding friction?
Static friction: keeps an object at rest from moving. Sliding friction: is a force that resists the motion of an object moving across a surface.
400
An empty wagon rolls easily, but a loaded wagon is more difficult to roll. Using your knowledge of Newton's 2nd Law, explain why this is so.
Newton's second law states that f = ma. An empty wagon has less mass, therefore it takes less force to accelerate. A loaded wagon has more mass and require more force to make it move.
400
Brianna starts a lawnmower moving across the yard by applying a force of 75 newtons on the handle of the mower. According to Newton's third law, the handle pushes back on Brianna with 75 newtons of force. Why does the mower move if the forces are equal and opposite?
The forces are acting on different objects and do not cancel one another. The force has a larger effect on the mower because Brianna has a larger mass, which is more difficult to accelerate. Therefore the mower is accelerated in the direction that Brianna is pushing.
500
Avinash is seated next to Eli. Which person is the origin?
Who is Eli?
500
Mr. Adriance leaves his classroom. He walks to Mrs. Trice's room at a speed of 5 m/s for 5 seconds. He then pauses at her room for 10 seconds. After this, he walks 20 meters to Ms. Nolan's room, and it takes him 15 seconds. Make either a speed vs. time graph OR a position vs. time graph for this.
Answers may vary?
500
The sum of all forces acting upon an object is called ____________.
What is the net force?
500
Sonic the hedgehog is known as the fastest thing alive. He is able to cover 10,000 meters in 3 seconds (He's been working out). What is is his speed? Sonic decides to make a trip around the moon. This trip is 20,006,000 meters. How long does it take him, if he is going at the same speed as before?
3333.3 m/s 6001.9 s = 100.03 min
500
A 400 lb man and woman weighing 120 lbs are seated in a car, going 80 mph. If the car were to instantly come to a stop by hitting another car, who would be more likely to fly through the windshield? Use newton's laws to explain your answer.
The woman. She has less mass, and thus would accelerate more and continue her motion forward.
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