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# Forces and Newton’s Laws: Practice - PowerPoint PPT Presentation

Forces and Newton’s Laws: Practice. Once again: everybody fights, nobody quits. Problem 1: OMG, they are so easy. Newton’s 1 st law: Newton’s 2 nd law: Newton’s 3 rd law: What is difference between mass and weight?. …And then….

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### Forces and Newton’s Laws: Practice

Once again: everybody fights, nobody quits

• Newton’s 1st law:

• Newton’s 2nd law:

• Newton’s 3rd law:

• What is difference between mass and weight?

• An airplane is flying at a constant speed. Draw a free body diagram of the plane below and include all the forces on the plane.

• A frisbee has been thrown and is maintaining a constant altitude. Draw a free body diagram below and show all the forces acting on the frisbee.

• A force of 20 N is acting at an angle of 500 from the horizontal.

• Find FX:

• Find FY:

• A force of 30 N is acting at an angle of 1500 from the horizontal.

• Find FX:

• Find FY:

• A pair of Freedom HS students find themselves having to push a stalled car. Frances Lee pushes with a force of 400 N and Kyle Cogar pushes with a force of 300 N. There is a 590N frictional force acting on the car.

• Draw a free body diagram for the system.

• Find the acceleration.

• a = 0.059m/s2

• Jordan Lee is on a raft. He exerts a force of 17N due east by rowing and the current exerts a force of 15 N at 670. Ignoring friction, what are the X- and Y-components of the raft’s acceleration if the total mass = 1300Kg?

• aX = 0.018m/s2, aY = 0.011m/s2

• Total magnitude of acceleration?

• A question from conceptual physics (you should totally be able to handle this one): A horse is pulling a cart. In doing so, the cart pulls on the horse with equal force. Why isn’t this a futile exercise? Why is that the horse is able to pull the cart?

• Scott Keeler grows up to become an astronaut. While working in space, he pushes on a satellite (11,000kg) with a force of 36 N. If his mass is 92 kg, what is the force on him from the satellite? What are both object’s acceleration?

• -36N, 0.0033 m/s2, -0.39 m/s2.

• What is the equation for the law of universal gravitation?

• What is the value of G?

• For two point masses of 20 and 25 kg separated by 3 m, what is the force of gravity they exert on each other?

• The mass of the earth is 5.9742 × 1024 kg and the mass of the sun is 1.99 X 10 30 kg. They are separated by a distance of 146 X 109 m. What is the magnitude of the gravitational attraction on the earth by the sun?

• 3.72 X 1022 N

• Saturn has an equatorial radius of 6 X 107 m and a mass of 5.67 X 1026 kg. What is the acceleration due to gravity at the equator of Saturn?

• 10.5 m/s2

• What is weight?

• What is the equation for weight on the surface of earth?

• What is the difference between weight and the force of gravity on an object?

• Suppose the force of gravity on an object is 20 N when it is sitting a distance X from the center of a second object. If X is doubled, how does the force of gravity change?

• A 12 kg object sits at rest on a table. What is its weight?

• What is the normal force on it from the table?

• If I push down on the object with an additional 6 N force, what is the normal force now from the table?

• If I pull up on the object with a 6 N force instead, what is the normal force from the table?

• What is apparent weight?

• What is the difference between apparent weight and actual weight?

• If a 300 N man is on an elevator that is accelerating upwards at 2 m/s2, what is the man’s apparent weight?

• What about if it is descending at 2 m/s2?

• What is the difference between static and kinetic friction?

• Write the equation for frictional force.

• If the normal force is 40 N and the coefficient of friction is 0.3, what is the frictional force?

• State the conditions for equilibrium.

• Travis Risinger is leaning at an angle of 450 against a wall. Name all the forces at work in this system. What is the net force on Travis?

• Can you have equilibrium at constant velocity?

• A system of masses and a pulley is show below. If there is no friction, what is the acceleration in the system?

• What is the coefficient of static friction required to keep the system at rest?

m1 = 2 kg

m2 = 3 kg

• An object is moved from sea level to the top of Mount Everest. Which changes: mass, weight, both, or neither?

• Object 1 weighs twice as much as object 2 at the same spot on earth. Would the same be true at the same place on Mars?

• A box is stationary on an elevator floor. Because of static friction, a force is required to get the box moving horizontally. Rank the force necessary for the situations when the elevator is stationary, accelerating downwards and accelerating upwards. Explain.

• Two bottle rockets are launched, one pointed straight up and one pointed horizontally. Ignoring friction and air resistance, which experiences the greater acceleration? Explain.

• A rollercoaster is accelerated from rest to 45 m/s in 7sec. The total mass of the coaster plus riders is 5.5 X 103 kg. What is the average net force exerted on the coaster?