4. A stone is projected vertically upwards. Which of the following has a NON-zero value at the maximum height?

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1 Physics Test Construction (30marks) Section A MCQ (10 marks) 1. A box of mass 2 kg travels at 3 ms -1 constant speed when it is being pushed horizontally on a rough surface by a 4 N force. What is the acceleration of the box when the force is increased to 6 N? A. 0 ms B. *1 ms -1 C. 2 ms -1 D. 4 ms 2. A box is being pushed horizontally along a rough surface and a constant acceleration is achieved. If the push is stopped, the box will A. *slows down and finally stop. B. continues to move at constant speed. C. accelerate at a lower rate. D. stops immediately. 3. A particle moving at a constant speed of 5 ms -1 is being acted on by two 10 N forces as shown in fig 1. The particle will A. stops immediately. -1 B. *continues to move at 5 ms C. slows down and gradually stop. D. increases its speed gradually. Fig 1 4. A stone is projected vertically upwards. Which of the following has a NON-zero value at the maximum height? A. *Acceleration B. Net force C. Velocity D. Air resistance 1

2 5. A man standing in a stationary lift releases a stone. The stone takes t seconds to reach the floor of the lift. If the lift is moving downwards with constant velocity instead of being stationary, A) the stone takes a time less than t seconds to reach the floor B) *the stone also takes a time of t seconds to reach the floor. C) the stone takes a time greater than t seconds to reach the floor. D) The stone may or may not reach the ground depending on the speed of the lift. 6. What will you feel about your weight when you are in a lift moving downwards with increasing velocity? A) The weight increases B) *The weight decreases C) The weight remains unchanged D) We feel weightless 7. The student is conducting an experiment on a toy car. The collected data were displayed on the graph (Fig 2) below. From this graph, what conclusion can he make from the graph? Fig 2 A) The net force on the car was constant B) *The net force on the car increased at a constant rate C) The acceleration of the car was constant D) The mass of the car increased at a constant rate 2

3 8. A homeowner pushes a lawn mower across a horizontal patch of grass with a constant speed by applying a force P. The arrows in Fig 3 correctly indicate the directions but not necessarily the magnitudes of the various forces on the lawn mower. Which of the following relations among the various force magnitudes, W, f, N, P is CORRECT? A) *P>f and N>W B) P<f and N=W C) P>f and N<W D) P<f and N>W Fig 3 9. The graph (Fig 4) shows the relationship between the mass of a number of rubber stoppers and their resulting weight on some far-off planet. The slope of the graph is a representation of the: Fig 4 A. Mass of stoppers B. Density of stoppers C. Volume of stoppers D. *Acceleration of stoppers 3

4 10. A lift of mass 200 kg starts moving down from rest. The variation of its velocity for 8 seconds is shown in the adjoining velocity time graph (Fig 5). What is the tension in the supporting wire during the 7 th second? A. *5500 N B N C N D N Fig 5 4

5 Section B Short answer question (10marks) 11. A spacecraft of mass 7000kg was on a mission to Mars for water discovery. Initially, it started travelling at a constant velocity of 3000m/s, however, seeing a meteoroid approaching, it ignited one of the side booster and changed its course of direction but continued to travel at a constant velocity of 4000m/s after the boosters stopped. Upon reaching Mars, it gradually decreased its velocity and came to a halt. A. What is the net force acting on the spacecraft initially when it is travelling at 3000m/s? Explain. [1m] B. Is there a change in the acceleration of the spacecraft during and after the booster ignition? Explain i. During: [1m] ii. After: [1m] 5

6 C. Upon reaching Mars, a crew suggested that to halt the spacecraft, a parachute should be opened at the back, do you agree with his idea, why? If not, what would you suggest?[2m] 12. The figure below shows a wooden block with a mass of 2kg being pulled with a force of 2N on a rough surface. The wooden block does not move because of friction. Fig 6 A. Draw and state the frictional force exerted on the wooden block in Fig 6 shown above. [1m] B. When the wooden block is pulled with a force of 5N, the block moves with a constant speed. i. What is the net force acting on the wooden block? [1m] ii. What is the frictional force exerted on the wooden block now? [1m] 6

7 C. State a way where the frictional force CAN be increased between the block and the floor. Give an example where increasing the friction between surfaces is useful. [2m] 7

8 Section C Long question (10marks) 13. Amy is travelling on a plane of 10000kg. It is constant speed, 7000m above the ground. Suddenly, all engines stopped and the plane starts to fall freely. The graph below shows how the downward speed of the plane varies with time. Take gravitational acceleration as g= 9.8ms -2 Fig 7 A. Draw and state the names of the downward and upward forces acting on the plane figure below when it is falling. [2m] B. State the initial value of the acceleration of the plane when all engine stopped. [1m] 8

9 C. Explain why the acceleration decreases from X to Y and remains constant after passing Y. [2m] D. Suggest a situation where the maximum downward speed would increase.[1m] E. Amy does not want to die and a thought comes to her mind. Since the plane is decreasing in height, she could probably jump off the plane when it is about to reach the ground as shown in Fig 8. Assuming the plane did not explode or crush her, do you think Amy s idea is feasible? Explain. [2m] Ground Fig 8 9

10 F. While Amy is pondering, the plane reaches its terminal velocity and suddenly, Superman fly pass. He flies to the bottom of the plane and start applying an upward force. Calculate the force Superman has to apply just to stop the plane from falling further in a short period of 10s, assuming the terminal velocity of the plane is 200m/s. [2m] Reference: MCQs are taken from Longman 1001 Physics MCQs for O Level Peng Yeon, Tan Q12 modified from Physics for GCE 'O' level theory workbook Loo, Wan Yong. Q 11 and Q13 are self-made questions 10

11 Physics marking scheme Section A MCQ 1. B 2. A 3. B 4. A 5. B 6. B 7. B 8. A 9. D 10. A Section B Structured a A. Net force = 0N and Constant velocity means no net force acting on the spacecraft. [B1] B. i. Yes. And Booster caused a change in the direction and the final velocity, which resulted in a change in acceleration. [B1] ii. No. and Booster stopped and spacecraft travelled at constant velocity with no net force acting on it. [B1] C. Do not agree, since space has got no atmosphere to resist the motion of the spacecraft. [B1] Fire another booster in the opposite direction of the motion of spacecraft. [B1] A. 2N [B1] B. i. Net force = 0N [B1] ii. Frictional force = 5N [B1] C. Apply a force perpendicular on the block perpendicular to the ground or changing to a rougher surface material of the block or the floor. [B1] Any reasonable examples, like soles of shoes, anti-slip materials along the stairs etc [B1]

12 Section C Long question 13. A. Correct labelling [B1] and Correct arrows [B1] Air resistance B. 9.8ms -2 [B1] Gravitational force C. The air resistance increases with the speed of the object. [B1] This causes the downward resultant force to decrease with time from X to Y.[B1] Hence the acceleration decreases D. When the air density decreases or in the absence of air. [B1] E. Not feasible [B1] Just before reaching the ground, Amy s velocity would be the same as the terminal velocity of the plane. A sudden change in the velocity will result in a great impact or impulse. [B1] F. Upward net force by Superman = mass of aeroplane x acceleration upwards [M1] = x (200/10) = N [A1]

13 MCQ Analysis Q3: A particle moving at a constant speed of 5 ms -1 is being acted on by two 10 N forces as shown in fig 1. The particle will Fig 1 A. stops immediately. B. *continues to move in the side direction at 5 ms C. slows down and gradually stop. D. Jumps upwards at 5 ms -1 Distracters: A: Misconceptions of zero net force = zero velocity C: Since net force is zero, particle should slow down from its initial velocity of 5 ms -1. D: Misconceptions on the addition of vectors. -1 Q4: A stone is projected vertically upwards. Which of the following has a NON-zero value at the maximum height? Distracters: A. *Acceleration B. Net force C. Velocity D. Air resistance B: Since stone is projected upwards, should have a net force acting upwards C: Most will know velocity is zero at max height, therefore mixing up with option A, thinking acceleration is zero too D: Since particle is travelling mid way, air resistance should continue be acting on it

14 Q8: A homeowner pushes a lawn mower across a horizontal patch of grass with a constant speed by applying a force P. The arrows in Fig 3 correctly indicate the directions but not necessarily the magnitudes of the various forces on the lawn mower. Which of the following relations among the various force magnitudes, W, f, N, P is CORRECT? A) *P>f and N>W B) P=f and N=W C) P>f and N<W D) P<f and N>W Fig 3 Distracters: B: Since moving forward with constant speed, no net force, therefore P=f and normal reaction is always equal to the weight of object C: since the mower is pushed downwards W must be greater than N. Thinking that N is always the same as the original weight of the object D: Since mower is moving forward, therefore P<f.

15 3. Dynamics Content Learning Outcomes/Topic(s) Cognitive level Higher Order Thinking Skills Total marks Knowledge Comprehension Application Analyzing Generating Evaluating (a) describe the effect of balanced and unbalanced forces on a body 13B[1m] Q7[1m] Q11Bii[1m] Q13D[2m] Q4 [1m] Q5[1m] 7 (b) describe the ways in which a force may change the motion of a body 11Bi[1m] 13F[2m] Q3[1m] Q11C[1m] 5 (c) identify forces acting on an object and draw free body diagram(s) representing the forces acting on the object (for cases involving forces acting in at most 2 dimensions) (d) solve problems for a static point mass under the action of 3 forces for 2- dimensional cases (e) recall the relationship resultant force = mass x acceleration Q9[1m] Q11A[1m] Q12A[1m] Q13A[1m] 13C[2m] 4 Q1[1m] Q10[1m] Q6[1m] Q8[1m] 2 13E[2m] 6 (f) explain the effects of friction on the Q12Bi[1m] Q2[1m] 12C[2m] motion of a body Q12Bii[1m] 13D[1m] 6 Total Total Percentage 10% 26.7% 16.6% 26.7% 10% 10% 100%