SPHY000 Assignment 2
University of Limpopo Department of Physics SPHY000 Assignment 2
- A truck is travelling at a constant velocity along a straight road. As it travels up a steep hill t slows down uniformly. Which ONE of the following velocity vs. time graphs best represents the motion of the car?
A truck is travelling at a constant velocity of 10 m·s^{−1} when the driver sees child 50 m in front of him in the road. He hits the brakes to stop the truck, and the truck decelerates at a rate of 1.25 m·s^{−2}. His reaction time to hit the brakes is 0.5 seconds.
- What distance will the truck travel before hitting the brakes?
A) 50.0 m B) 45.0 m C) 5.0 m D) 40.0 m E) None of them
- How long it will take the truck to stop after hitting the brakes?
A) 0.5 s B) 8.5 s C) 8.0 s D) 7.5 s E) None of them
- Will the truck hit the child?
- No, the truck will not hit the child as it will stop 0.5 m before the child.
- Yes, the truck will hit the child and it will stop 50 m after.
- No, the truck will not hit the child as it will stop 5.0 m before the child.
- Yes, it will hit the child and it will stop 45.0 m after.
- None of the above
Consider the motion of an object illustrated by the velocity vs time graph as shown in the figure below.
- The distance versus time graph for the motion between E and F is as shown in
- The total distance travelled by the object from A to F is
A) 150 m B) 210 m C) 90.00 m D) 69.75 m E) None of them
- The displacement of the object from A to F is
A) 150 m B) 210 m C) 90.00 m D) 69.75 m E) None of them
- The motion of the object from B to C is as explained in
- The object travelled to the left with an acceleration of 10.0 m/s^{2} for a distance of 20.0 m for 2 s.
- The object travelled to the left with an acceleration of -10.0 m/s^{2} for a distance of 20 m for 2 s.
- The object travelled from the left with an acceleration of 10.0 m/s^{2} for a distance of 20 m for 2 s.
- The object travelled from the left with an acceleration of -10.0 m/s^{2} for a distance of 20 m for 2 s.
- None of them
- The acceleration between E and F is
A) – 00 m/s^{2} B) 10.00 m/s^{2 }C) 7.50 m/s^{2 } D) 3.75 m/s^{2} E) None of them
An SPHS000 female student determined to test the law of gravity for herself walks off a skyscraper 250 m high, stopwatch in her hand, and starts her free fall (zero initial velocity). Four and half seconds later, Superman arrives at the scene and dives off the roof to save the student.
- The time taken by the student to fall to the ground is
A) 5.00 s B) 2.82 s C) 7.14 s D) 60.0 s E) None of them
- In order for Superman to catch the lady student just before she reaches the ground, his initial velocity must be
A) 75 m/s B) 9.81 m/s C) 92.56 m/s D) 30 m/s E) None of them
A student is on the roof of the physics building, 10.0 m above the ground as shown in the accompanying figure 2 below. His Physics lecturer, who is 1.8 m tall, is walking alongside the building at a constant speed of 1.20 m/s. The student wishes to drop an egg on his lecturer’s head.
- After how long will the egg hit the lecturer’s head?
A) 1.67 s B) 1.29 s C) 4.00 s D) 3.00 s E) None of them
- How far away (horizontally), should the lecturer be when the student releases the egg?
A) 8.20 m B) 11.80 m C) 1.55 m D) 1.8 m E) None of them
- What will be the velocity of the egg when it hits the lecturer?
A) 12.68 m/s B) 1.20 m/s C) 13.88 m/s D) 11.48 m/s E) None of them
- If the egg thrown by the student had missed the lecturer, what would be the velocity of the egg just before it hits the ground?
A) 12.68 m/s B) 30.0 m/s C) 1.20 m/s D) 14.01 m/s E) None of them
- What would be the time taken by the egg to reach the ground?
A) 1.29 s B) 1.43 s C) 3.06 s D) 0.12 s E) None of them
The coordinates of a particle moving in the xy-plane are given by
x = 12.0t – 6.0t^{2}
y = 6t + 12.0t^{2} ,
where x and y are in metres, and t in seconds.
- The position of the particle at t = 2.0 s
A) 0 m at the origin B) 60.0 m along the +ve y axis C) 12.0 m along +ve x axis D) 48.0 m 45^{o} clockwise from the +ve x axis E) None of them
- The magnitude of the initial velocity of the particle is
A) 18.0 m/s B) 6.0 m/s C) 13.4 m/s D) 180 m/s E) None of them
- The instantaneous acceleration at t = 3.0 s is
A) 26.8 m.s^{-2 }68^{o} above the +ve x axis B) -12.0 m.s^{-2 }along the –ve y axis
C) 8 m.s^{-2 }68^{o} below the +ve y axis D) 12.0 m.s^{-2} 68^{o} below the +ve y axis E) None of them
The position of a particle between t = 0 and t = 2.00 s is given by
x(t) = (3.00m/^{3})t^{3} - (10.00m/s^{2})t^{2} + (9.00m/s)t-3
- The displacement of the particle between time t = 0 and t = 2 s is
A) -5.00 m B) 5.00 m C) 2.00 m D) -3.00 m E) None of them
- The average velocity of the particle between time t = 1.00 and t = 3.00 s is
- A) 8.00 m /s B)16.00 m/s C) 9.00 m/s D) 30.00 m/s E) None of them
- The instantaneous velocity at time t = 2 s is
A) –50 m /s B) 30.00 m/s C) 9.00 m/s D) 5.00 m/s E) None of them
- The values of time(s) t between t = 0 and t = 2.00 s when the velocity of the particle is instantaneously at rest are
A) 0 s B) 0.63 and 1.60 s C) 2.00 s D) 0 and 2.00 s E) None of them
- The acceleration(s) at each time calculated in the question above are
A) – 20.00 m/s^{2 }B) 16.00 m/s^{2 } C) – 8.66 & 8.80 m/s^{2 } D) – 20.00 & 16 ms^{2 }E) None of them
- The average acceleration of the particle between time t = 2 and t = 3 s is
A) 16.00 m/s^{2 }B) 25.0 m/s^{2 } C) 9.81 ms^{2 } D) 32.00 m/s^{2 } E) None of them
- A cricket ball is thrown vertically upwards and reaches a height of 30 m above the ground. On the way down it gets stuck in a tree 12 m above the ground. What is the resultant displacement of the ball?
A) 10 m downwards B) 12 m upwards C) 18 m downwards D) 42 m upwards E) 12 m downwards
- Tom is leaning on the railing of a tall building. His cellphone drops out of his hands and falls to the ground. Which of the following combinations of velocity and acceleration for the motion of the cellphone is correct?
Velocity |
cceleration | |
A) |
Increases |
Remains constant |
B) |
Decreases |
Increases |
C) |
Increases |
Decreases |
D) |
Remains constant |
Remains constant |
E) |
None of the above |
None of the above |
The height of a tower is 50 m. A stone is thrown vertically upwards from the top of the tower and it took 5.0 s to return to the position at which it was thrown.
- The velocity at which the stone was thrown is
A) 41.2 m/s B) 24.5 m/s C) 39.8 m/s D) 30.0 m/s E) None of them
- The maximum height reached by the stone.
A) 0.66 m B) 346.1 m C) 86.5 m D) 30. 6 m E) None of them
- The velocity at which the stone hits the ground.
A) 41.2 m/s B) 24.5 m/s C) 39.8 m/s D) 30.0 m/s E) None of them
- The total time that the stone was in air.
A) 4.05 s B) 14.05 s C) 10.00 s D) 6.55 s E) None of them
During the 2010 Soccer World Cup played here in South Africa, Simphiwe Tshabalala scored a beautiful long range shot when Bafana Bafana was playing against Mexico in the opening game. After kicking the ball, it touched the goal-line (at ground level) 30 m from where he kicked it, and the maximum height reached by the ball was 8.0 m.
- The time at which the ball reached this maximum height is
A) 2.20 s B) 4.20 s C) 3.30 s D) 1.28 s E) None of them
- The angle at which Tshabalala kicked the ball relative to the ground is
A) 53.4^{o} B) 43.1^{o } C) 46.9^{o } D) 36.6^{o} E) None of them
- The vertical component of the initial velocity, v_{oy }is
A) 11.29 m/s B) 11.72 m/s C) 12.53 m/s D) 17.16 m/s E) None of them
- The initial velocity at which he kicked the ball is
A) 11.29 m/s B) 11.72 m/s C) 12.53 m/s D) 17.16 m/s E) None of them
- Both the vertical and horizontal components of the velocities of the ball after 1.0 s are
A) 11.29 & 17.16 m/s B) 11.72 & 2.72 m/s C) 2.72 & 11.72 m/s D) 17.16 & 12.53 m/s E) None of them
Venus Williams whilst training for the Swiss Open tennis tournament hits a tennis ball with a speed of 20.00 m/s at an angle of 42^{o }to the horizontal. She strikes the ball directly towards a wall which is a horizontal distance of 22 m from the point of release of the ball.
- The time it takes the ball in the air before it strikes the wall is
A) 3.12 s B) 1.36 s C) 1.51 s D) 2.41 s E) None of them
- The velocity of the ball as it strikes the wall is
A) 13.38 m/s B)14.86 m/s C) 20.00 m/s D) 1.18 m/s E) None of them
- Whether the ball did pass the highest point (on its trajectory) or not when it strikes the wall, how far away was it from the highest point?
A) 9.05 m B) 0.07 m C) 1.79 m D) 9.12 m E) None of them
A block of mass m_{1} (10 kg) on a smooth, horizontal surface is connected to a second mass m_{2} (4 kg) by a light cord over a light, frictionless pulley as shown in figure 3 below. A force F of magnitude 80 N is applied to mass m_{1} as shown. the applied force F is at an angle of 30^{o} with the horizontal.
- For mass m_{2}, ∑F_{y}=
A) T – m_{2}g = m_{2}a B) T – m_{2}g = m_{2}a C) m_{2}g – T = 0 D) m_{2}g – T = m_{2}a E) None of them
- For block of mass m_{1}, ∑F_{x }=
A) Fcosθ – f_{k} – T = m_{1}a B) Fcosθ – T = m_{1}a C) Fsinθ + f_{k} – T = m_{1}a D) Fcosθ – f_{k} – T = (m_{1 + }m_{2})a E) None of them
- For block of mass m_{1}, ∑F_{y }=
A) Fsinθ – f_{k} – T = m_{1}a B) N – m_{1}g = 0 C) Fsinθ + N – m_{1}g = 0 D) Fsinθ – m_{1}g = 0 E) None of them
- The acceleration of the system is
A) 2.17 m.s^{-2 }B) 9.81 m.s^{-2} C) 2.22 m.s^{-2 }D) 27 m.s^{-2 }E) None of them
- The tension T of the system is
A) 29.4 N B) 42.24 N C) 47.92 N D) 63.3 N E) None of them
If m_{1} now rests on a rough surface and the coefficient of kinetic friction between m_{1} and the surface is 0.24,
- The new acceleration of the system is
A) 21.84 m.s^{-2 }B) 9.81 m.s^{-2} C) 2.22 m.s^{-2} D) 4.91 m.s^{-2 }E) None of them
- The new tension T of the system is
A) 29.4 N B) 24.1 N C) 39.24 N D) 63.3 N E) None of them
- A car of mass m is on an icy driveway inclined at an angle θ as in figure 4 below. Find the acceleration of the car, assuming the driveway is frictionless.
gcosθ B. gsinθ C. mgsinθ D. mgcosθ E. None of the above
Two blocks of masses m_{1} = 10 kg and m_{2} = 5 kg, are placed in contact with each other on a frictionless, horizontal surface as in figure 5. A constant horizontal force F is applied to 10 kg as shown.
- The magnitude of the acceleration of the system is
0.07 F B. 12.9 F C. 6.0F D. 15 F E. None of the above
- Consider the atwood machine in figure 6. Determine the acceleration of the two masses, where m_{1} is 5 kg and m_{2} is 12 kg.
1.04 m/s^{2 }B. 2.04 m/s^{2} C. 3.04 m/s^{2} D. 4.04 m/s^{2} E. None of the above
- Determine the tension of atwood machine in question 49.
17.06 N B. 30.23 N C. 40.23 N D. 69.25 E. None of the above
Question 51 to question 54 are based on this statement: Block of mass 2.00 kg is released from rest at h = 0.500 m above the surface of a table, at the top of a θ = 30.0 ^{o} inclined as shown in figure 7. The frictionless incline is fixed on a table of height H = 2.00 m.
- Determine the acceleration of the block as it slides down the incline.
6.82 m/s^{2 } B. 4.91 m/s^{2} C. 10.33 m/s^{2} D. 2.76 m/s^{2} E. None of the above
- What is the velocity of the block as it leaves the incline?
3.13 m/s at 30 ^{o} above the horizontal B. 12.2 m/s at 60 ^{o} above the horizontal
3.13 m/s at 30 ^{o} below the horizontal D. 12.2 m/s at 60 ^{o} below the horizontal E. None of the above
- How far from the table will the block hit the floor?
3.20 m B. 1.35 m C. 7.12 m D. 0.20 m E. None of the above
- What time interval elapses between when the block is released and when it hits the floor?
A. 14 s B. 7.66 s C. 2.22 s D. 12.31 s E. None of the above
- Does the mass of the block affect any of the above calculations?
A. No B. Yes C. Question 51 only D. Question 52 only E. Question 53 only
Question 56 and question 57 are based on this statement: A woman at an airport is pulling her 20-kg suitcase at constant speed by pulling on a strap at an angle θ above the horizontal as in figure 8. She pulls on a strap with a 35-N force and the friction force on the suitcase is 20 N.
- What angle does the strap make with the horizontal?
A. 55.2^{o} B. 60.01^{o} C. 32.4^{o} D. 83.7^{o} E. None of the above
- What normal force does the ground exert on the suitcase?
A. 100.6 N B. 190.1 N C. 167.3 N D. 100.6 N E. None of the above
- A 3.0 kg mass is moving in a plane with its x and y coordinates given by
x = 5t^{2} - 1 and
y = 3t^{3} + 2,
where x and y are given in meters while t is in seconds. Find the magnitude of the net force acting on this mass at t = 2.0 s.
A. 400.0 N B. 413.2 N C. 123.5 N D. 270.1 N E. None of the above
- A net horizontal force F = A+Bt^{3} acts on a 2 kg object, where A = 4.0 N and B = 2.0 N/s^{3}. What is the horizontal velocity of this object 4 seconds after it starts from rest?
72 m/s B. 74 m/s C. 133 m/s D. 264 m/s E. None of the above
Question 60 and question 61 based on this statement: The three blocks in figure 9 below are connected by light strings that pass over frictionless pulleys. The acceleration of the system is 2.0 m/s^{2} to the left and the surface are rough.
- Find the tensions in the strings.
A. 55.0 N, 20.0 N B. 78.0 N, 35.9 N C. 70.0 N, 25.0 N D. 89.5 N, 28.9 N E. None of the above
- Find the coefficient of kinetic friction between blocks and surfaces.
A. 0.655 B. 0.076 C. 1.032 D. 0.182 E. None of the above
Question 62 and question 63 are based on this statement: Two blocks of mass m_{1} = 4 kg and m_{2} =7 kg are connected by a light string that passes over a frictionless pulley as shown in figure 7 below.
- 62. Find the acceleration of each block.
A. 3.12 m/s^{2} B. 2.50 m/s^{2} C. 4.31 m/s^{2} D. 1.53 m/s^{2} E. None of the above
- Find the tension in the string.
A. 17.5 N B. 28.6 N C. 45.3 N D. 23.6 N E. None of the above
- The system described in figure 10 is observed to have an acceleration of 1.5 m/s^{2} when the inclines are rough. Assume the coefficients of kinetic friction between each block and the inclines are the same. Find coefficient of kinetic friction in the string.
A. 0.4 B. 0.2 C. 0.3 D. 0.5 E. None of the above
- From question 64, find the tension in the string
12.0 N B. 24.2 N C. 32.5 N D. 41.3 N E. None of the above
- Three forces, given by F_{1} = (- 2.00 i + 2.00 j) N, F_{2} = (5.00 i - 4.00 j) N, and F_{3} = - 45.0 i N act on an object to give it an acceleration of magnitude 3.75 m/s^{2}. What is the direction of the acceleration?
A. 2.7^{o } B. 1.4^{o} C. 3.8^{o} D. 5.2^{o } E. None of the above
- In which quadrant is the acceleration or the resultant force?
A. 1^{st } B. 2^{nd} C. 3^{rd} D. 4^{th} E. None of the above
- What is the magnitude of the resultant force?
A. 42 N B. 44 N C. 2 N D. 1768 N E. None of the above