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AP Physics Review Ch 4 – Forces and Newton’s Laws of Motion. Be able to apply Newton’s three laws to conceptual questions
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AP Physics Review Ch 4 – Forces and Newton’s Laws of Motion • Be able to apply Newton’s three laws to conceptual questions • Be able to draw free body diagrams and determine the magnitude of each force; from your free body diagram, write an equations for both the x and y axes; if the object is in equilibrium, then F=0; if the object is accelerating, then F=ma • Be able to calculate the normal force (not necessarily equal to mg) • Be able to solve force problems involving friction (fN) • Be able to solve tension problems including objects hanging from cables at various angles and frictionless pulley problems • Be able to calculate the force of gravity and the acceleration due to gravity on different planets • Know the definition of inertia and how it is measured • Be able to identify action-reaction pairs and know that they are always equal • Useful equations to know:
A Martian lander is approaching the surface. It is slowing its descent by firing its rocket motor. Which is the correct free-body diagram for the lander?
A Martian lander is approaching the surface. It is slowing its descent by firing its rocket motor. Which is the correct free-body diagram for the lander?
A satellite orbits the earth with constant speed at height above the surface equal to the earth’s radius. The magnitude of the satellite’s acceleration is • gon earth. • gon earth. • gon earth. • 2gon earth. • 4gon earth.
gon earth. • gon earth. • gon earth. • 2gon earth. • 4gon earth. A satellite orbits the earth with constant speed at height above the surface equal to the earth’s radius. The magnitude of the satellite’s acceleration is
The figure shows a binary star system. The mass of star 2 is twice the mass of star 1. Compared to , the magnitude of the force is • one quarter as big. • half as big. • twice as big. • four times as big. • the same size.
The figure shows a binary star system. The mass of star 2 is twice the mass of star 1. Compared to , the magnitude of the force is • one quarter as big. • half as big. • twice as big. • four times as big. • the same size.
A planet has 4 times the mass of the earth, but the acceleration due to gravity on the planet’s surface is the same as on the earth’s surface. The planet’s radius is • Re. • Re. • Re. • 2Re. • 4Re.
A planet has 4 times the mass of the earth, but the acceleration due to gravity on the planet’s surface is the same as on the earth’s surface. The planet’s radius is • Re. • Re. • Re. • 2Re. • 4Re.
An elevator that has descended from the 50th floor is coming to a halt at the 1st floor. As it does, your apparent weight is • More than your true weight. • Less than your true weight. • Equal to your true weight. • Zero.
An elevator that has descended from the 50th floor is coming to a halt at the 1st floor. As it does, your apparent weight is • More than your true weight. • Less than your true weight. • Equal to your true weight. • Zero.
A rock is attached to a string and hangs from the ceiling of an elevator. As the elevator is moving downward and slowing to a stop, the tension in the string is • greater than the weight of the rock. • less than the weight of the rock. • equal to the weight of the rock. • Zero.
A rock is attached to a string and hangs from the ceiling of an elevator. As the elevator is moving downward and slowing to a stop, the tension in the string is • greater than the weight of the rock. • less than the weight of the rock. • equal to the weight of the rock. • Zero.
All three 50 kg blocks are at rest. Is the tension in rope 2 greater than, less than or equal to the tension in rope 1? • greater than • less than • equal to
All three 50 kg blocks are at rest. Is the tension in rope 2 greater than, less than or equal to the tension in rope 1? • greater than • less than • equal to
In the figure to the right is the tension in the string greater than, less than, or equal to the weight of block B? • Greater than • Less than • Equal to
In the figure to the right is the tension in the string greater than, less than, or equal to the weight of block B? • Greater than • Less than • Equal to
A small car is pushing a larger truck that has a dead battery. The mass of the truck is larger than the mass of the car. Which of the following statements is true? • The car exerts a force on the truck but the truck doesn’t exert a force on the car. • The car exerts a larger force on the truck than the truck exerts on the car. • The car exerts the same amount of force on the truck as the truck exerts on the car. • The truck exerts a larger force on the car than the car exerts on the truck. • The truck exerts a force on the car but the car doesn’t exert a force on the truck.
A small car is pushing a larger truck that has a dead battery. The mass of the truck is larger than the mass of the car. Which of the following statements is true? • The car exerts a force on the truck but the truck doesn’t exert a force on the car. • The car exerts a larger force on the truck than the truck exerts on the car. • The car exerts the same amount of force on the truck as the truck exerts on the car. • The truck exerts a larger force on the car than the car exerts on the truck. • The truck exerts a force on the car but the car doesn’t exert a force on the truck.
Is the tension in rope 2 greater than, less than, or equal to the tension in rope 1? • greater than rope 2 • less than than rope 2 • equal to rope 2
Is the tension in rope 2 greater than, less than, or equal to the tension in rope 1? • greater than rope 2 • less than than rope 2 • equal to rope 2
A B Consider two identical blocks, one resting on a flat surface, and the other resting on an incline. For which case is the normal force greater? (A) case A (B) case B (C) both the same (N = mg) (D) both the same (0 < N < mg) (E) both the same (N = 0)
Three blocks of mass 3m, 2m, and m are connected by strings and pulled with constant acceleration a. What is the relationship between the tension in each of the strings? a (A) T1 > T2 > T3 (B) T1 < T2 < T3 (C) T1 = T2 = T3 (D) all tensions are zero (E) tensions are random T2 T3 T1 3m 2m m
Case 1 Case 2 Below you see two cases: a physics student pulling or pushing a sled with a force F which is applied at an angle q. In which case is the normal force greater? (A) case 1 (B) case 2 (C) it’s the same for both (D) depends on the magnitude of the force F (E) depends on the ice surface
m2 m1 In the Atwood machine shown in the diagram, if m1 = 0.40 kg and m2 = 0.60 kg, what is the magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley.) (A) 5.3 m/s2 (B) 3.9 m/s2 (C) 0.98 m/s2 (D) 2.0 m/s2
What is the acceleration of the 4 kg mass if there is no friction between the 2kg mass and the horizontal surface? (A) 0.0 m/s2 (B) 2.0 m/s2 (C) 4.0 m/s2 (D) 6.7 m/s2 (E) 10 m/s2
What is the acceleration of the 4 kg mass if there is no friction between the 2kg mass and the horizontal surface? (A) 0.0 m/s2 (B) 2.0 m/s2 (C) 4.0 m/s2 (D) 6.7 m/s2 (E) 10 m/s2
37o 37o A traffic light of weight 100 N is supported by two ropes as shown in the diagram. What are the tensions in the ropes? (A) 50 N (B) 63 N (C) 66 N (D) 83 N