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Name______________ Regents PhysicsUnit 4: Forces and Newton’s Laws of Motion Mr. MullerUnit 4: Forces and Newton’s Laws of Motion1. Base your answer to the following questions on the information below.A stream is 30 meters wide and its current flows southward at 1.5 meters per second. A toy boat is launched with a velocity of 2.0 meters per second eastward from the west bank of the stream.What is the magnitude of the boat’s resultant velocity as it crosses the stream?0.5 m/s2.5 m/s3.0 m/s3.5 m/s2. A child walks 5.0 meters north, then 4.0 meters east, and finally 2.0 meters south. What is the magnitude of the resultant displacement of the child after the entire walk?1) 0.5 m 2) 2.5 m 3)3.0 m 4)11.0 m3. As the angle between two concurrent forces decreases, the magnitude of the force required to produce equilibrium1) decreases2) increases3) remains the same4. A 6.0 – newton force and an 8.0 – newton force act concurrently on a point, as the angle between these forces increases from 0 degrees to 90 degrees, the magnitude of their resultant 1) decreases2) increases3) remains the same5. A 5.0 – newton force and an 7.0 – newton force act concurrently on a point. As the angle between these forces increases from 0 degrees to 180 degrees, the magnitude of the resultant of the two forces changes from 1) 0.0 N to 12.0 N2) 2.0 N to 12.0 N3) 12.0 N to 0.0 N6. the diagram represents a 5.0 – newton force and a 12-newton force acting on point P. The resultant of the two forces as a magnitude of1) 5.0 N2) 7.0 N3) 12 N4) 13 N7. the diagram below shows a resultant vector RWhich diagram best represents a pair of component vectors, A and B, that would combine to form resultant vector R?8. A 3 newton force and a 4 newton force are acting concurrently on a point. Which force could not produce equilibrium with these two forces?1) 1 N2) 7 N3) 9 N4) 4 N9. The diagram below represents a force vector, A and resultant vector, R.Weight vs. Mass1. Define mass and weight:Mass: Weight:2. What is another name for weight?3. Why does ass for a given object remain constant, but its weight can change?4. A 150.0 lb person wants to know what their mass and wight (in Newtons).A) convert their weight (in lbs.) to Newtons (1 N = 0.22 pounds)B) Determine their mass.5. A person has a mass of 90.0 kg on Earth. If the person goes to Planet Muller, where the acceleration due to gravity is 3.50 m/s/s, what is the person’s weight? What is the person’s mass on Planet Muller?6. An astronaut has a mass of 85.0 kg. The astronaut goes to the moon and has a wight of 136 N. what is the acceleration due to gravity on the moon?Balanced vs. Unbalanced ForcesReview: An object at rest ... ;An object in motion .... ;unless ....1.The amount of force required to keep a 6-kg object moving with a constant velocity of 2 m/s is __ N.a. 0.333b. 2c. 3d. 6e. 12f. ... nonsense! A force is NOT required to keep an object in motion.2.Renatta Oyle is having car troubles. She is notorious for the trail of oil drops that she leaves on the streets of Glenview. Observe the following oil traces and indicate whether Renatta's car is being acted upon by an unbalanced force. Give a reason for your answers.Unbalanced Force?a.Reason:Yes or Nob.Reason:Yes or Noc. Reason:Yes or No3.Each one of the dot diagrams in question #2 can be matched to a force diagram below. The force diagrams depict the individual forces acting upon the car by a vector arrow. The arrow direction represents the direction of the force. The arrow length represents the strength of the force. Match the dot diagrams from #2 to a force diagram; not every force diagram needs to be matched.Dot Diagram(s): _______Dot Diagram(s): _______Dot Diagram(s): _______4.If the net force acting upon an object is 0 N, then the object MUST ____. Circle one answer.a. be movingb. be acceleratingc. be at restd. be moving with a constant speed in the same directione. either c or d.5.These graphs describe the motion of Carson Busses at various times during his trip to school. Is Carson's vehicle being acted upon by an unbalanced force? Give a reason in terms of a description of what the car is doing (speeding up, slowing down, or constant velocity).0+-VelocityTime0+-VelocityTime0+-VelocityTime0+-VelocityTime0+-VelocityTime0+-VelocityTimeUnbalanced Force?Yes or No?Reason/Description:Unbalanced Force?Yes or No?Reason/Description: Unbalanced Force?Yes or No?Reason/Description:6.A free-body diagrams show all the individual forces acting upon an object. The net force is the vector sum of all these forces (∑F). Determine the net force and state if there is an acceleration.a.b.c.Fgrav = 20 NFnorm = 20 NFgrav = 25 NFair = 40 NFgrav = 40 NFnorm = 40 NFfrict = 10 NFgrav = 20 NFnorm = 20 NFgrav = 25 NFair = 40 NFgrav = 40 NFnorm = 40 NFfrict = 10 N∑F = ________________∑F = ________________∑F = ________________Accel'n? Yes or NoAccel'n? Yes or NoAccel'n? Yes or No7.During an in-class discussion, Anna Litical suggests to her lab partner that the dot diagram for the motion of the object in #6b could beAnna's partner objects, arguing that the object in #6b could not have any horizontal motion if there are only vertical forces acting upon it. Who is right? ____________ Explain.8.During an in-class discussion, Aaron Agin asserts that the object in #6a must be moving to the left since the only horizontal force acting upon it is a "left-ward" force. Is he right? ______ Explain.9.The diagrams below depict the magnitude and direction of the individual forces acting upon an object. Which objects could be moving to the right? Circle all that apply.1615044topFree-Body Diagrams and Newton’s 2nd Law1. Free-body diagrams for four situations are shown below. For each situation determine the horizontal and vertical force acting upon the object. Also, if there is a net force, determine the direction of the acceleration. 2. Free-body diagrams for four situations are shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known. Analyze each situation individually and determine the magnitude of the unknown forces. 4. A 1,500 kg car slams on its brakes and comes to a rest in 4.50 s. If 10,000 N of force is applied to the car for it to stop, calculate the initial speed of the car. (Draw a Free-body diagram first)5. A 100. Kg car starts from rest and reaches a speed of 20.0 m/s over a distance of 15.0 m. Calculate the net force acting on the car.6. A person sits on a sled which has a combined mass of 90.0 kg, If the sled is being pulled to the right with a force of 50.0 N and friction applies 50.0 N of resistance, is the sled accelerating? Explain. (Draw a free-body diagram first)7. Based on the previous question, if the sled is now pulled with a force of 70.0 N instead, is the sled accelerating? If so, calculate the acceleration. (Draw a free-body diagram first)8. A 7.00 N force acts to the left on a 1.50 kg box while an unknown force acts to the right while on top of a flat surface. The box accelerates to the right at 3.33 m/s/s.A) Draw a free body diagram of the forces acting on the box.B) Determine the magnitude of the unknown force acting to the right on the box.9. Three forces act on a 2.00 kg box that is on a flat surface causing it to accelerate at 2.50 m/s/s to the right. If one of the forces is 10.0 N left and another one is 12.0 N to the right, determine the magnitude and direction of the third force. (Hint: find net force first).10. A 5.00 N force acts to left on a 2.00 kg box while a 10.0 N force at an angle of 30.0 degrees from the horizontal acts to the right.A) Determine the net horizontal force (magnitude and direction) acting on the box. (Draw a Free-Body Diagram First)B) Determine the horizontal acceleration of the box (magnitude and direction).11. A 1500 kg car is pulled to the left with a force of 150 N and to the right with a force of 300 N to the right. Calculate the magnitude and direction of the acceleration of the car? (Draw a Free-Body diagram first)12. Find the magnitude and direction of the acceleration of the box.13. A 50.0 kg block is pulled by three forces. Force 1 pulls with 15.0 N at an angle of 30.0 degrees to the right, Force 2 pulls with a 10.0 N force directly to the right and Force 3 pulls with a force of 5.00 N directly to the right.A) Find the net horizontal force on the block (draw a free body diagram first)B) Find the acceleration of the blockFriction1. Draw a free body diagram and calculate the force of friction of a 20.0 kg steel block moving a constant speed on a steel level surface (Hint use reference tables)A) Draw a free body diagram of all the forces acting on the box.B) What is the net force acting on the box? (give magnitude with direction)C) Calculate the acceleration of the box? (give magnitude with direction)D) Calculate the coefficient of friction between the box and the floor.3. A 70.0 Kg person on waxed skies is moving along a flat snow covered ground at 5.00 m/s until coming to a stop.A) Draw a free-body diagram of all the forces acting on the person. (Be careful, is there an applied force in this case??)B) Calculate the force of friction acting on the person.C) What is the net horizontal force of the person?D) calculate the acceleration of the skier. (give magnitude and direction)E) Calculate the distance the skier covers until coming to a stop.4. What is the minimum force needed to start the motion of a 3.00 x 103 kg car with rubber wheels that is at rest on dry asphalt?5. What would be the minimum force needed to keep the 3.00 x 103 car with rubber wheels moving at a constant speed on dry asphalt?Additional Newton’s Laws and Friction ProblemsDirections: Solve for the problems below using Newton’s Second Law of Motion and the friction equation. Complete a free-body diagram for each problem.1. A refrigerator has a mass of 119 kg and is initially at rest on a horizontal floor. It takes a horizontal force of 428 N to set it in motion. Once the refrigerator is moving, it takes a horizontal force of 401 N to keep it moving at a constant velocity.A) Calculate the coefficient of static friction between the refrigerator and the floor.B) Calculate the coefficient of kinetic friction between the refrigerator and the floor.2. A student wishes to pull a 200 N steel box across on a steel surface at a constant acceleration of 1.50 m/s/s.A) Calculate the amount of friction between the box and the surface.B) Calculate the net force acting on the box.C) Calculate the force needed to be applied in order for it to accelerate it at this rate.3. A clerk moves a box of cans down an aisle by pulling horizontally on a rope attached to the box. The clerk pulls with a force of 190 N. The box has a mass of 35.0 kg and the coefficient of kinetic friction between the box and floor is 0.450A) Calculate the amount of friction between the box and the floor.B) Calculate the acceleration of the box.4. A 2.00 kg waxed ski slides down a small snowy hill. Once the ski hits the bottom of the hill it starts to slow down on a horizontal surface until it comes to a complete stop. What is the acceleration of the sled as it comes to a stop?5. A 58.1 kg person has a weight of 570 N after getting off a bathroom scale in their apartment. The person then takes the scale and places it in the elevator where they live and gets on the scale. They then push the button for the elevator to go down and once the elevator begins to go downward, the scale suddenly reads 525N. What is the acceleration of the elevator going downward?6. A 20.0 kg block is being pulled to the right across a level rough surface by a force of 120 N causing it to accelerate at 0.750 m/s/s. Calculate the force of friction and coefficient of friction. ................
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