Physics final - study

16. A 60-kg woman runs up a flight of stairs having a rise of 4.0 m in a time of 4.2 s. What average power did she supply?

(560 W)

14. A stone is thrown with an initial speed of 15 m/s at an angle of 53 above the horizontal from the top of a 35 m building. If g = 9.8 m/s2 and air resistance is negligible, then what is the speed of the rock as it hits the ground?

(30 m/s)

16. A rock is thrown straight up with an initial velocity of 24.5 m/s.What maximum height will the rock reach before starting to fall downward? Take acceleration due to gravity as 9.80 m/s2.

(30.6 m)

8. A 15-kg block rests on a level frictionless surface and is attached by a light string to a 5.0-kg hanging mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s2, what is the tension in the connecting string?

(37 N)

3. A 1 200-kg automobile moving at 25 m/s has the brakes applied with a deceleration of 8.0 m/s2. How far does the car travel before it stops?

(39 m)

9. A boxcar of mass 200 tons at rest becomes uncoupled on a 2.5 grade. If the track is considered to be frictionless, what speed does the boxcar have after 10 seconds?

(4.3 m/s)

6. A 20-N crate starting at rest slides down a rough 5.0-m long ramp, inclined at 25 with the horizontal. 20 J of energy is lost to friction. What will be the speed of the crate at the bottom of the incline?

(4.7 m/s)

7. A pile driver drives a post into the ground. The mass of the pile driver is 2 500 kg and it is dropped through a height of 8.0 m on each stroke. If the resisting force of the ground is 4.0 106 N, how far is the post driven in on each stroke?

(4.9 cm)

18. A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250-kg crate. What is the acceleration of the crate if the 750-N force is maintained after the crate begins to move and the coefficient of kinetic friction is 0.12?

(1.8 m/s2)

A 7.0-kg bowling ball experiences a net force of 5.0 N. What will be its acceleration?

(0.71 m/s2)

7. A 2 500-kg truck moving at 10.00 m/s strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at 7.00 m/s. What was the mass of the struck car?

(1 070 kg)

13. A 500-N tightrope walker stands at the center of the rope such that each half of the rope makes an angle of 10.0 with the horizontal. What is the tension in the rope?

(1 440 N)

3. Two ropes are attached to a 40-kg object. The first rope applies a force of 25 N and the second, 40 N. If the two ropes are perpendicular to each other, what is the resultant acceleration of the object?

(1.2 m/s2)

18. A baseball is released at rest from the top of the Washington Monument. It hits the ground after falling for 6.0 s. What was the height from which the ball was dropped? Ignore air resistance.

(1.8 x 102 m)

5. A 2 000-kg sailboat experiences an eastward force of 3 000 N by the ocean tide and a wind force against its sails with magnitude of 6 000 N directed toward the northwest (45 N of W). What is the direction of the resultant acceleration?

(74 N of W)

7. John throws a baseball from the outfield from shoulder height, at an initial velocity of 29.4 m/s at an initial angle of 30.0 with respect to the horizontal. The ball is in its trajectory for a total interval of 3.00 s before the third baseman catches it. Ignore the air resistance. What is the ball's horizontal displacement?

(76.4 m)

6. A jogger runs halfway around a circular path with a radius of 60 m. What, respectively, are the magnitude of the displacement and the distance jogged?

(120 m, 188 m)

8. A railroad freight car, mass 15 000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 50 000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 20 000-kg car is preserved in the two-coupled cars after collision?

(23%)

12. A 5.0 kg box slides up a 10 m long frictionless incline at an angle of 20 degrees with the horizontal pushed by a 40 Newton force parallel to the incline. What is the change in kinetic energy?

(232 J)

A hiker walks 200 m west and then walks 100 m north. In what direction is her resulting displacement?

(26.6 N of W)

A European sports car dealer claims that his car will accelerate at a constant rate from rest to 100km/h in 8.00s. If so, what is the acceration?

3.47m/s (Squared)

A railroad train travels forward along a straight track at 80m/s for 1,000m and then travels at 50m/s for the next 1,000m. What is the average velocity

61.5ms

20. Alex, parked by the side of an east-west road, is watching car P, which is moving in a westerly direction. Barbara, driving east at a speed 52 km/h, watches the same car. Take the easterly direction as positive. If Alex measures a speed of 78 km/h for car P, what velocity will Barbara measure?

(-130 km/h)

5. A hill is 100 m long and makes an angle of 12 with the horizontal. As a 50-kg jogger runs up the hill, how much work does gravity do on the jogger?

(10 000 J)

26. Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is another light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s2 what is the tension in the connecting string between the blocks?

(10 N)

9. A baseball thrown from the outfield is released from shoulder height at an initial velocity of 29.4 m/s at an initial angle of 30.0 with respect to the horizontal. What is the maximum vertical displacement that the ball reaches during its trajectory?

(11.0 m)

m/s to the NORTHWEST. What is the total momentum of the system?

(20.3 kg m/s at an angle of 69.7 degrees NORTH of WEST)

22. A sled weighs 100 N. It is held in place on a frictionless 20 slope by a rope attached to a stake at the top; the rope is parallel to the slope. Find the tension in the rope.

(34 N)

wall with a velocity of 4.0 m/s. What is the change in momentum of the ball?

(36 kg m/s)

20. Doug hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.050, how far will the puck slide before stopping?

(37 m)

13. A 20 kg box slides down a 12.0 m long frictionless incline at an angle of 30 degrees with the horizontal. A force of 50 N is applied to the box to try to pull it up the incline. The applied force makes an angle of 10 degrees to the incline and above the incline. What is the increase in the kinetic energy of the box?

(585 J)

14. A drag racer starts from rest and accelerates at 10 m/s2 for the entire distance of 400 m (1/4 mile). What is the velocity of the race car at the end of the run?

(89 m/s)

A cheetah can run at approximately 100km/hr and a gazelle at 80 km/hr. If both animals are running at full speed, with the gazelle 70m ahead, how long before the cheetah catches its prey?

12.6s

Which one, temperature, velocity, acceleration or displacement, is not a vector Quantity?

Temperature

2. If the kinetic energy of a ball is doubled, what happens to the momentum of the ball?

(1.41 times larger)

9. I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?

(0.29 J)

2. An astronaut applies a force of 500 N to an asteroid and it accelerates at 7.00 m/s2. What is the asteroid's mass?

(71 kg)

17. A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250-kg crate. If g = 9.8 m/s2, what is the coefficient of static friction?

(0.31)

A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface. If the cart accelerates at 2.0 m/s2, then what is the work done by the force of friction as it acts to retard the motion of the cart?

(-900 J)

An object moves 20m east in 30s and then returns to its starting point taking an additional 50s. If west is chosen as the positive direction, what is the average speed of the object?

(.050 m/s)

19. A 100-kg box is placed on a ramp. As one end of the ramp is raised, the box begins to move downward just as the angle of inclination reaches 15. What is the coefficient of static friction between box and ramp?

(0.27)

21. Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another. The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 2.0 m/s2. What is the magnitude of the force exerted on the right cube by the middle cube in this case?

(12 N)

6. Two blocks, joined by a string, have masses of 6.0 and 9.0 kg. They rest on a frictionless horizontal surface. A 2nd string, attached only to the 9-kg block, has horizontal force = 30 N applied to it. Both blocks accelerate. Find the tension in the string between the blocks.

(12 N)

27. Two blocks of masses 20 kg and 8.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is a second light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s2, what is the tension in the second string attached to the 8-kg mass?

(14 N)

19. A rock, released at rest from the top of a tower, hits the ground after 1.5 s. What is the speed of the rock as it hits the ground? Ignore air resistance.

(15 m/s)

11. A ball is pushed with an initial velocity of 4.0 m/s. The ball rolls down a hill with a constant acceleration of 1.6 m/s2. The ball reaches the bottom of the hill in 8.0 s. What is the ball's velocity at the bottom of the hill?

(17 m/s)

16. A block of mass 5.00 kg rests on a horizontal surface where the coefficient of sliding kinetic friction between the two is 0.200. A string attached to the block is pulled horizontally, resulting in a 2.00-m/s2 acceleration by the block. Find the tension in the string.

(19.8 N)

19. A plane is moving due north, directly towards its destination. Its airspeed is 200 mph. A constant breeze is blowing from west to east at 40 mph. At what rate is the plane moving north?

(196 mph)

8. A girl and her bicycle have a total mass of 40.0 kg. At the top of the hill her speed is 5.0 m/s, and her speed doubles as she rides down the hill. The hill is 10.0 m high and 100 m long. How much kinetic energy and potential energy is lost to friction?

(2 420 J)

4. A 2 000-kg sailboat experiences an eastward force of 3 000 N by the ocean tide and a wind force against its sails with magnitude of 6 000 N directed toward the northwest (45 N of W). What is the magnitude of the resultant acceleration?

(2.2 m/s2)

15. A Cessna aircraft has a lift-off speed of 120 km/hr. What minimum constant acceleration does this require if the aircraft is to be airborne after a take-off run of 240 m?

(2.31 m/s2)

20. Human reaction time is usually about 0.20 s. If your lab partner holds a ruler between your finger and thumb and releases it without warning, how far can you expect the ruler to fall before you catch it?

(20 cm)

17. A boat moves at 10.0 m/s relative to the water. If the boat is in a river where the current is 2.00 m/s, how long does it take the boat to make a complete round trip of 1 000 m upstream followed by a 1 000-m trip downstream?

(208 s)

30. Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another. The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 2.0 m/s2. What is the magnitude of the force exerted on the middle cube by the left cube in this case?

(24 N)

13. When a drag strip vehicle reaches a velocity of 60 m/s, it begins a negative acceleration by releasing a drag chute and applying its brakes. While reducing its velocity back to zero, its acceleration along a straight line path is a constant 7.5 m/s2. What displacement does it undergo during this deceleration period?

(240 m)

9. A a vs. t graph is drawn for a car moving in one direction. The graph shows a horizontal line at a = 5 m/s2 from t = 0 s to t = 5 s. What is the velocity of the ball at t = 5 s? Assume the car is initially at rest.

(25 m/s)

24. A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30 above the horizontal, and the tension in the rope is 100 N. What is the normal force of the floor on the box?

(250 N)

28. An elevator weighing 20 000 N is supported by a steel cable. What is the tension in the cable when the elevator is being accelerated upward at a rate of 3.00 m/s2?

(26 100 N)

A 30 kg mass falls from a height of 4.0 m. What is the momentum of the mass just before it hits the ground?

(265.6 kg m/s)

13. A stone is thrown with an initial speed of 15 m/s at an angle of 53 above the horizontal from the top of a 35 m building. If g = 9.8 m/s2 and air resistance is negligible, then what is the magnitude of the vertical velocity component of the rock as it hits the ground?

(29 m/s)

20. A 100-W light bulb is left on for 10.0 hours. Over this period of time, how much energy was used by the bulb?

(3 600 000 J)

6. During a snowball fight two balls with masses of 0.4 and 0.6 kg, respectively, are thrown in such a manner that they meet head-on and combine to form a single mass. The magnitude of initial velocity for each is 15 m/s. What is the speed of the 1.0-kg mass immediately after collision?

(3 m/s)

4. A 10.0-kg box starts at rest and slides 3.5 m down a ramp inclined at an angle of 10 with the horizontal. If there is no friction between the ramp surface and crate, what is the velocity of the crate at the bottom of the ramp?

(3.5 m/s)

15. A spring-powered dart gun is un-stretched and has a spring constant 12.0 N/m. The spring is compressed by 8.0 cm and a 5.0 gram projectile is placed in the gun. What is the velocity of the projectile when it is shot from the gun?

(3.92 m/s)

15. A stone is thrown with an initial speed of 15 m/s at an angle of 53 above the horizontal from the top of a 35 m building. If g = 9.8 m/s2 and air resistance is negligible, what is the magnitude of the horizontal displacement of the rock?

(38 m)

15. A 20-kg traffic light hangs midway on a cable between two poles 40 meters apart. If the sag in the cable is 0.40 meters, what is the tension in each side of the cable?

(4 900 N)

17. A rock is thrown straight up with an initial velocity of 19.6 m/s. What time interval elapses between the rock's being thrown and its return to the original launch point?

(4.00 s)

18. A 1 000-kg sports car accelerates from zero to 25 m/s in 7.5 s. What is the average power delivered by the automobile engine?

(41.7 kW)

9. A 7.0-kg bowling ball strikes a 2.0-kg pin. The pin flies forward with a velocity of 6.0 m/s; the ball continues forward at 4.0 m/s. What was the original velocity of the ball?

(5.7 m/s)

12. A stone is thrown at an angle of 30 above the horizontal from the top edge of a cliff with an initial speed of 12 m/s. A stop watch measures the stone's trajectory time from top of cliff to bottom to be 5.6 s. How far out from the cliff's edge does the stone travel horizontally? Ignore air resistance.

(58 m)

17. Water flows over a section of Niagara Falls at a rate of 1.20 106 kg/s and falls 50.0 m. What is the power dissipated by the waterfall?

(588 MW)

11. A 5 000-N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T1. Cable 2 applies a force upward and to the left at an angle of 37.0 to the negative x axis and has a tension, T2. What is the tension, T1?

(6 640 N)

10. As a 3.0-kg bucket is being lowered into a 10-m-deep well, starting from the top, the tension in the rope is 9.8 N. What is the acceleration of the bucket?

(6.5 m/s2 downward)

7. A 10-kg mass and a 2.0-kg mass are connected by a light string over a massless, frictionless pulley. If g = 9.8 m/s2, what is the acceleration of the system when released?

(6.5 m/s2)

4. Alex throws a 0.15-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s, and just after is 3.5 m/s. If the ball is in contact with the floor for 0.025 s, what is the magnitude of the average force applied by the floor on the ball?

(60 N)

16. A jet airliner moving at 500 mph due east moves into a region where the wind is blowing at 120 mph in a direction 30.0 north of east. What is the new velocity and direction of the aircraft?

(607 mph, 5.67 N of E)

3. The following force vectors act on an object: i) 50.0 newtons at 45.0 north of east and ii) 25.0 newtons at 30.0 south of east. What is the magnitude of the resultant force and its angle relative to the easterly direction?

(61.4 newton at 21.8)

14. The graph shows the force on an object as it moves a distance x. What is the work done by the force when the object moves from 0.0 m to 10.0 m?

(64 J)

12. A cart is given an initial velocity of 5.0 m/s and experiences a constant acceleration of 2.0 m/s2. What is the magnitude of the cart's displacement during the first 6.0 s of its motion?

(66 m)

25. A 120 Newton box is at rest on an incline of 35 degrees. The surface of the incline is frictionless and a rope is attached to the box and exerts a force on the box that is 10 degree above the incline. What is the force exerted by the rope on the box?

(69.9 N)

2. A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision?

(7/16)

29. Find the tension in an elevator cable if the 1 000-kg elevator is descending with an acceleration of 1.8 m/s2, downward.

(8 000 N)

12. A 5 000-N weight is suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T1. Cable 2 applies a force upward and to the left at an angle of 37.0 to the negative x axis and has a tension, T2. Find T2.

(8 310 N)

14. A 500-N tightrope walker stands at the center of the rope. If the rope can withstand a tension of 1 800 N without breaking, what is the minimum angle the rope can make with the horizontal?

(8)

2. A taxicab moves five blocks due north, five blocks due east, and another two blocks due north. Assume all blocks are of equal size. What is the magnitude of the taxi's displacement, start to finish?

(8.6 blocks)

11. A horizontal force is applied to a 4.0 kg box. The box starts from rest moves a horizontal distance of 8.0 meters and obtains a velocity of 6.0 m/s. The system is frictionless. What is the horizontal force?

(9 N)

18. A river flows due east at 3.0 m/s. A boat crosses the 300-m-wide river by maintaining a constant velocity of 10 m/s due north relative to the water. If no correction is made for the current, how far downstream does the boat move by the time it reaches the far shore?

(90 m)

4. A string attached to an airborne kite is maintained at an angle of 40 with the horizontal. If a total of 120 m of string is reeled in while bringing the kite back to the ground, what is the horizontal displacement of the kite in the process? Assume the kite string doesn't sag.

(92 m)

23. A sled weighs 100 N. It is held in place on a frictionless 20 slope by a rope attached to a stake at the top; the rope is parallel to the slope. What is the normal force of the slope acting on the sled?

(94 N)

5. Jack pulls a sled across a level field by exerting a force of 110 N at an angle of 30 with the ground. What are the parallel and perpendicular components, respectively, of this force with respect to the ground?

(95 N, 55 N)

11. A stone is thrown at an angle of 30 above the horizontal from the top edge of a cliff with an initial speed of 12 m/s. A stop watch measures the stone's trajectory time from top of cliff to bottom to be 5.6 s. What is the height of the cliff?

(Ignore air resistance. (120 m)

19. A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, what happens to the power delivered to it by the force? It remains the same, increases, or decreases?

(Increases)

10. A baseball thrown from the outfield is released from shoulder height at an initial velocity of 29.4 m/s at an initial angle of 30.0 with respect to the horizontal. It is being caught by the third baseman. At what point is the ball's speed at a minimum and what is the minimum speed? Ignore air resistance.

(at the top of the trajectory. 25.5 m/s)

10. A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position. Under the same compression d, the spring is now used to launch a mass of 2m. How high does this second mass rise?

(h/2)

8. A v vs. t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 5 s the acceleration of the ball is zero. What is the velocity of the ball at t = 5 s?

(the velocity of the ball is not changing)

8. A baseball thrown from the outfield is released from shoulder height at an initial velocity of 29.4 m/s at an initial angle of 30.0 with respect to the horizontal. If it is in its trajectory for a total of 3.00 s before being caught by the third baseman, what is the ball's net vertical displacement during its 3-s trajectory?

(zero)

An object moves 20m east in 30s and then returns to its starting point taking an additional 50s. If west is chosen as the objective direction, what is the sign associated with the average velocity of the object?

0, no sign

10. A 50-g ball traveling at 25.0 m/s is bounced off a brick wall and rebounds at 22.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the average acceleration of the ball during this time interval?

13 400 m/s2)