Newton's law of motion Questions and Answers

9 A hot air balloon has just lifted off and is rising at the con stant rate of 2 0 m s Suddenly one of the passengers realizes she has left her camera on the ground A friend picks it up and tosses it straight upward with an initial speed of 13 m s If the passenger is 2 5 m above her friend when the camera is tossed how high is she when the camera reaches her

A person exerts a force of 250 N on a large crate but the crate does not move What would the total force from both the crate and the person be

37 A 13 00 tg black is pushed up block is pushed up a friction less in cheed place that makes an angle of a with the horizontal direction What force is needed to move the block with constant speed Assume that the force is parallel to the surface of the plane in N

10 Which types of forces may change the total momentum of a system external forces only internal forces and external forces internal forces only

9 Which statement represents Newton s second law O Net force equals the product of mass and momentum O Net force equals momentum O Net force equals the product of the change in momentum and mass O Net force equals the change in momentum over time

12 A girl of mass 40 kg throws a ball of mass 0 65 kg against a wall The ball strikes the wall horizontally with a speed of 30 m s and it bounces back with this same speed ball is in contact with the wall 0 05 s What is the average force exerted on the wall by the ball O 400 N O 780 N O 10 000 N 40 000 N

A force of 126 N pulls due west on a body and a second force pulls N 36 4 degW The resultar force is 171 2 N Find the magnitude of the second force and the direction of the resultant 1 1 Select an answer The direction of the resultant is deg

1 Two people of identical mass are running towards each other Person B is running at 3 m s If Person A and Person B collide who exerts the greater force upon impact Person A exerts the greater force because they have the greater momentum before the collision Not enough information to determine Person A exerts the same force on Person B as Person B exerts on Person A 5 points ESTION 3 Using Person A and Person B from Question 2 what is the final momentum after they collide Both Person A and Person B have a mass of 75 kg Let the final momentum be a positive answer Assume they are running in a straight line C75 Newtons seconds C525 Newtons seconds 75 m s 05 Newtons seconds

stretch is 13 0 cm Assume an ideal spring a Determine the spring constant T2 C2 b The spring mass system is compressed a certain amount past it s equilibrium to accelerate it at 14 0 m s downwards How much was the spring compressed to accelerate the mass at this rate T4 C2

An elevator is suspended by a cable and moves upward Which of the following free diagrams best represents the forces acting on the elevator FT is the force of tension supplied by the cable Ft Fe O a A O b B Odc O d D B FH Fe C Fe D FT E FN

25 A pendulum of mass 1 0 kg is suspended from the roof of a car travelling on a level road An observer in the car notices that the pendulum string makes an angle of 10 with the vertical What is the acceleration of the car 4

Course Contents HW Bonus slides down an inclined plane Timer Notes wc6p22 5e A block with mass m 20 7 kg slides down an inclined plane of slope angle 30 3 with a constant velocity It is then projected up the same plane with an initial spe 55 m s How far up the incline will the block move before coming to rest M

24 A boy on a toboggan is sliding down a snow covered hillside The boy and toboggan together have a mass of 50 kg and the slope is at an angle of 30 to the horizontal Find the boy s acceleration considering the following 10 30 a if there is no friction b if the coefficient of kinetic friction is 0 15

26 The sign for Pierre s restaurant has a mass of 82 kg It is held out from the wall by a light horizontal steel rod which supports no weight and a wire at 40 to the horizontal as illustrated Find the tension in the wire and the compression in the steel rod 5 40 Chez Pierre tension compression

A 2 00kg ball traveling at 5 00 m s to the left runs into a 3 50kg ball traveling at 4 00 m s to the right The ball traveling left bounces off going 2 50 m s to the right a What is the momentum of the system before the collision b What is the momentum of the system after the collision c What is the velocity of the other ball after the collision

Describe the input and output trade off between these two inclined planes

Submit Answer Tries 0 8 What is the magnitude of the acceleration y Submit Answer Tries 0 8 0 Bc5p78 Five forces pull on the 2 1 kg box in the figure with F1 3 4 N F2 13 0 N at an angle of 30 F3 4 9 N F4 12 0 N and F5 17 0 N Find the box s acceleration in u ector notation i component of the acceleration 1 2m s 2 Submit Answer Incorrect Tries 1 8 Previous Tries component of the acceleration X

27 A projectile is launched at initial speed vo at initial angle 0 For which value of 0 is the maximum height of the projectile the greatest O 90 O 0 45 O 180

4p56 A 51 4 kg high school student hangs from an overhead bar with both hands What is the tension in each arm if the bar is gripped with both arms raised vertically overhead Submit Answer Tries 0 8 What is the tension in each arm when the arms make an angle of 38 00 with respect to the vertical

nesc4p62 problem A B 30 Figure 4 43 Problems 4 61 and 4 62 p62 What is the force exerted by the string on the wall at point A in the figure if the suspended fish has mass m 0 50 k Submit Answer Tries 0 8

The table gives the x and y components of two forces F and F2 Force F1 F2 x component 49 N 25 N The magnitude of the resultant force is Your Answer N y component 57 N 49 N

16 A mass of 20 kg is suspended from a ceiling by two lengths of rope that make angles of 30 and 45 with the ceiling Determine the tension in each of the ropes

4 36 Which of Newton s Laws is best O 2nd Law Fnet ma O1st Law Law of Inertia forces on one another

7 12 When do you use Fg mg as opposed to Newton s Universal Law of Gravitation Fg G m1 m2 r 2

Birdman is flying horizontally at a speed of 38 m s and a height of 71 m Birdman releases a turd directly above the start of the field How far from the start of the field should the robot hold the bucket to catch it Show all work here

A spring stretches 0 169 m when a 0 378 kg mass is gently suspended from it as in Fig 11 3b The spring is then set up horizontally with the 0 368 kg mass resting on a frictionless table as in Fig 11 5 The mass is pulled so that the spring is stretched 0 214 m from the equilibrium point and released from rest Determine c the magnitude of the maximum velocity Vmax

A spring stretches 0 190 m when a 0 268 kg mass is gently suspended from it as in Fig 11 3b The spring is then set up horizontally with the 0 423 kg mass resting on a frictionless table as in Fig 11 5 The mass is pulled so that the spring is stretched 0 293 m from the equilibrium point and released from rest Determine c the magnitude of the maximum velocity Vmax

h R Q hrw8c11p8 A solid marble of mass m 35 kg and radius r 4 cm will roll without slipping along the loop the loop track shown in the figure if it is released from rest somewhe straight section of track From what minimum height h above the bottom of the track must the marble be released to ensure that it does not leave the track at the top of the loop radius of the loop the loop is R 1 05 m Submit Answer Tries 0 10 If the marble is released from height 6R above the bottom of the track what is the horizontal component of the force acting on it at point Q

1 A block A with a mass of 25 0kg is tied to a string looped over a pulley and then tied to a block B with a mass of 10 0kg A B I a Draw the Free body diagram for both block A and block B b What is the acceleration of the system c What is the tension on the rope connecting them 2 A satellite with a mass of 125kg is in orbit at a distance of 3 00x106 m above the surface of the Earth

Two forces of 424 N and 591 N act on an object The angle between the forces is 47 Find the magnitude of the resultant and the angle that it makes with the larger force The magnitude of the resultant is approximately N Round to the nearest whole number as needed

A State whether the sentence or statement is TRUE or FALSE 1 The normal force FN that acts on an object is always equal in magnitude and opposite in direction to the gravitational force F that is acting on it 2 Friction always acts against an object s motion relative to the contact surface 3 When forces acting on an object are in equilibrium the object can still be moving 4 For an object sliding along a ramp the force of kinetic friction acting on the object increases as the angle of inclination of the ramp increases 5 A car accelerates from rest when a traffic light turns green A cup of coffee that was sitting on the dashboard of the car falls into the driver s lap The driver could rightly argue that the cup s apparent motion was due to its inertia It had a tendency to stay still and the car accelerated from beneath it 6 The sum of all the forces acting on a stationary object is the same as that acting on an object in uniform motion 7 For an object travelling with uniform circular motion its acceleration is always directed tangent to the circle 8 When a curve in the road is banked a component of the normal force contributes to the centripetal force

FR answers the question 9 When analyzing dynamics problems free body diagrams a should always be used b are more useful when analyzing horizontal forces than when analyzing vertical forces c should include only the forces that are directly responsible for the acceleration d should be used only when objects are accelerating e only apply to objects in equilibrium 10 The free body diagram of a block being pushed up a rough ramp is best represented by A B C D E FN F a zero app FK b 47 N F app he retter of une choI F F F c 82 N unal Des app Fr F A the statement of F app F 8 a A b B c C d D e E 11 A 24 kg traffic light is suspended from the midpoint of a cable suspended between two poles The angle between the cable and the pole is 80 at both poles The net force acting on the traffic light has a value of d 2 4 x 10 N e 4 6 x 10 N F app

h R B Q hrw8c11p8 A solid marble of mass m 35 kg and radius r 4 cm will roll without slipping along the loop the loop track shown in the figure if it is released from rest somewhere or straight section of track From what minimum height h above the bottom of the track must the marble be released to ensure that it does not leave the track at the top of the loop TH radius of the loop the loop is R 1 05 m Submit Answer Tries 0 10 If the marble is released from height 6R above the bottom of the track what is the horizontal component of the force acting on it at point Q

Course Contents HW12 uniform square sign 4 00 m bmit Answer Tries 0 10 at is the horizontal component of the force exerted by the wall on the rod Cable ubmit Answer Tries 0 10 at is the vertical component of the force exerted by the wall on the rod Hinge Rod H Perez 2 00 m DENTIST 2 00 m 2p28 A 175 kg uniform square sign 2 00 m on a side is hung from a 3 00 m rod of negligible mass A cable is attached to the end of the rod and to a point on the wall 4 00 m we the point where the rod is fixed to the wall see the figure What is the tension in the cable 3 00 m

In a physics lab a pendulum hung from the ceiling swings back and forth Suddenly the string breaks as the pendulum bob reaches its lowest point from the left Which arrow best represents the direction of the pendulum bob s velocity immediately after the string breaks 4 B 00 E B

A Force of 350N Slo W is applied to an object for 0 09 sec The object move with relocity lom S N after the Force is applied what is inital Velocity

1 An 8 Kg block 2 Kg block and 6 Kg block are placed on a level frictionless surface An applied force of 48 N acts on the 8 Kg block to move all three as shown in the figure below Determine the acceleration of the masses the normal force between the 8 Kg and 2 Kg surface Determine the force between the 2 Kg and 6 Kg surface FAP 48 N 8 Kg 2 Kg 6 Kg

A 0 80 kg ball was dropped from a height of 2 0 m above the rebounded to a height of 1 6 m The contact between the ball and the ground lasted for 0 045 s You must start with the equations in your Physics Reference Tables You may only use the answer to question 3 above as a starting point if you have already solved that problem a What was the impulse applied to the ball 907 70 93001 syslovs sni Answer 9 59 N s b What was the average net force on the ball

a Slied What was the impulse applied to the car hoogoth antros ori malo trigl 2 240 0 101 ni cool pups sdi Et noilesup msidorq or ballags setugm Answer 8000 N s b What was the average net force on the car as it came to a stop

4 Kristen uses a magnet to move a met l ball The ball has a mass of 0 12kg The magnet exerts a force of 3N which causes the ball to begin moving What is the acceleration of the ball when it begins to move Record and bubble your answer 00

A 6 00 kg block is in contact with a 4 00 kg block on a horizontal frictionless surface as shown in the figure The 6 00 kg block is being pushed by a horizontal 20 0 N force as shown What is the magnitude of the force that the 6 00 kg block exerts on the 4 00 kg block 20 0 N 04N 08 N 20 N OON O6N 6 00 kg 4 00 kg

A crane is lifting a concrete slab upwards at a constant speed The forces on the slab are The upward force from the crane cable is greater than the downward force of gravity on the slab The upward force from the crane cable equal to the downward force of gravity on the slab The upward force from the crane cable is smaller than the downward force of gravity on the slab None of the above

A force of 1 60 N is exerted on a 8 00 g rifle bullet What is the bullet s acceleration Enter your answer in m s m s

You throw a ball upwards The air resistance is negligible After the ball leaves your hand and before it reaches the ground the forces acting on the ball are O a constant force of gravity and a decreasing force upwards acting on the ball until it reaches the highest point O a decreasing force upwards acting on the ball until it reaches the highest point and no forces acting after that Ono forces acting on the ball during its free fall a constant force of gravity

A box is pushed across a smooth frictionless table and is sliding away from the person who delivered the push After the box lost contact with the hands of the person who was pushing it the forces acting on the box are Normal force from the table gravity and the force that keeps the box moving forward Normal force from the table and gravity Only the force that keeps the box moving forward Gravity and the force that keeps the box moving forward Only gravity

Problem 2 Two masses m 500 g and m 1 5 kg on a frictionless horizontal surface are connected by a light string A force F with magnitude 5 N is exerted on m2 to the right Assume the tension has the same magnitude at every point in the string and neglect air resistance m1 T m F a Since the masses are connected by a string they are constrained to move together Express this constraint as an equation relating the accelerations of the two masses b Draw free body diagrams for the two masses and write down the horizontal component of the net force on each mass c Use Newton s 2nd law and the constraint from part a to find the acceleration of both masses and the magnitude T of the tension in the string

20 minutes later a second bus travels the same road However this bus is full of passenger How will the full bus s acceleration rate compare to the empty bus from question 1 Describe your thinking below being sure to address all three variables in the equation above You do not need to show math in your answer 5 pts

Say an empty bus is traveling down the road when the driver sees a deer The brakes are able to apply 45 000 N of force to stop the 9000 kg bus Using the equation above calculate a value for the acceleration for the bus Show your work for these calculations below and be sure to include units 5 pts

2 A man slides down a pole with 500N of force The opposing friction is 200N a Draw the force diagram b Calculate the net force 3 A man and his wife push a refrigerator to the right The man pushes with 70N of force to the right and the woman pushes with 40N of force to the right The force of friction is 100N a Draw the force diagram b Calculate the net force c Does the refrigerator move How do you know 4 Mr Smith and his wife were trying to move their new chair Mr Smith pulls with a force of 30N while Mrs Smith pushes with a force of 25N in the same direction What is the net force 5 6 Draw a force diagram b Calculate the net force 61 N 192 N 545N 732 N 61 N 545 N 732 N I 7 A potted plant is being pushed across the floor to the right with 60N of force The frictional force against the pot is 12N a Draw a force diagram that matches this situation b Calculate the net force 8 A rock is falling through the sky The force of gravity on the rock is 650N The rock experiences 250N of force as it falls a Draw the force diagram that matches this situation b Calculate the net force

or a certain interval of time an object is acted on by a constant non zero force Which of the following statements is true for this interval of time Select all that apply The object is moving with constant velocity The object s velocity can only increase The object is at rest The object is accelerating The object s velocity changes