Phys 2A Midterm Exam 2024 Spring PDF

Phys 2A Midterm Exam 2024 Spring You have 50 minutes to finish 15 multiple-choice questions Please pick the best option in every question. Each question is one point. (1) Three forces are applied on an object as shown in (4) A cheetah accelerates f...

Phys 2A Midterm Exam 2024 Spring You have 50 minutes to finish 15 multiple-choice questions Please pick the best option in every question. Each question is one point. (1) Three forces are applied on an object as shown in (4) A cheetah accelerates from rest to 26 m/s in 3 the figure below. What is the magnitude of the net seconds. Assuming that the acceleration is constant, force (in N)? how far (in meters) does the cheetah move in this A. 1 B. 1.5 C. 2 D. 2.5 E. 3 process? A. 30 B. 32 C. 39 D. 42 E. 45 Answer: C (5) A fish jumps out of the water surface at point A with a speed of 2.5 m/s along the 45° direction above the horizontal. After a projectile motion, the fish gets back to the water at point B. What is the distance (in meters) between point A and point B? A. 0.34 B. 0.64 C. 0.45 D. 0.54 E. 0.78 Answer: B Answer: E (6) A scale used to weigh fish consists of a spring hung from a support. The spring's equilibrium length is 10.0 (2) Which figure(s) below depict an object that has cm. When a 4.0 kg fish is suspended from the end of negative acceleration? the spring, it stretches to a length of 13.4 cm. What is the spring constant k (in N/m) for this spring? A. 954 B. 1020 C. 1153 D. 1453 E. 1520 Answer: C (7) A ball of mass 1 kg is acted upon by only two forces: an upward tension of 40 N and its downward weight. What can you say about the block's motion? A. It must be moving upward. B. It must be moving downward. C. It must be at rest. D. It must be moving along a straight line. E. It could be moving in any direction or be instantaneously at rest. Answer: E A. Figure 1 B. Figure 2 C. Figure 3 D. Figure 4 E. Both Figure 3 and 4 (8) A spacecraft takes off from a planet with an Answer: E upward acceleration of 5.4 m/s2. The free-fall acceleration of that planet is g = 16.6 m/s2. What is the (3) A cross-country skier is skiing along at 8.0 m/s. apparent weight (in N) of a 70-kg astronaut during She stops pushing and simply glides along, slowing to takeoff? a reduced speed of 6.0 m/s after gliding for 5.0 m. A. 1540 B. 1200 C. 2100 D. 1870 E. 1650 What is the magnitude of her acceleration (in m/s2) as Answer: A she slows? A. 2.8 B. 3.0 C. 3.2 D. 3.4 E. 3.6 (9) A 1350 kg car traveling at a speed of 43 m/s skids Answer: A to a halt on wet concrete where the coefficient of 1 kinetic friction is µk = 0.37. How long (in meters) are (14) A car with a mass of 1500 kg is being towed by a the skid marks? rope held at a 20-degree angle to the horizontal. A A. 152 B. 275 C. 255 D. 75 E. 342 friction force of 320 N opposes the car’s motion. What Answer: C is the tension (in N) in the rope if the car goes from rest to 12 m/s in 10 s? (10) A sky diver is falling at a terminal velocity. Then A. 1529 B. 2710 C. 3214 D. 2450 E. 2256 she opens her parachute. Right after she opens her parachute, which of the statements below is wrong? A. The drag force becomes larger than her weight. B. She experiences an upward acceleration. C. She is no longer at a terminal velocity. D. She continues to accelerate downward. E. Her speed decreases. Answer: D Answer: E (11) A horse has a top speed of 24 m/s. After it starts running, its acceleration drops exponentially with a (15) Two blocks with masses M1 = 1 kg and M2 = 2 time constant of 4.2 s. What is its speed (in m/s) at 2 s kg hang one under the other. They undergo an upward after it starts running? acceleration a = 5.2 m/s2. What is the difference (in N) A. 7.4 B. 8.6 C. 9.1 D. 10.2 E. 12. between T1 and T2 (that is, the value of T1 – T2)? Answer: C A. 5 B. 10 C. 12 D. 15 E. 20 (12) An object weights 100 N on the earth. If this object is on a planet, which has twice the mass of the Earth and also twice the radius of the Earth, what is the new weight of the object? A. 400 N B. 200 N C. 100 N D. 50 N E. 25 N Answer: D (13) A box of mass 10.0 kg is suspended a distance of h = 1.00 m below the ceiling by two cables that make equal angles with the ceiling. Each cable has a length of l = 1.50 m (see the Figure). What is the tension T (in N) in each of the cables? A. 73.5 B. 76.8 C. 84.7 D. 92.7 E. 102.2 Answer: D Answer: A 2 Formula sheet: (s = x or y for horizonal or vertical motions) Motion with exponentially decreasing acceleration: 𝑎(𝑡) = 𝑎)*+ 𝑒 -./0 ; 𝑣(𝑡) = 𝑣)*+ (1 − 𝑒 -./0 ); 𝑣)*+ = 𝜏𝑎)*+; 𝛥𝑥(𝑡) = 𝑣)*+ (𝑡 − 𝜏 + 𝜏𝑒 -./0 ) 89: Reynolds number = ; = >)F Drag force due to inertial force: 𝐷 = 𝐶@ 𝜌𝐴𝑣 > ; 𝑣.CD) = E > GH 8I N Drag force due to viscous force for a spherical object of radius r: 𝐷 = 6𝜋𝜂𝑟𝑣; 𝑣.CD) = OP;D ) = Viscous-force-dominated motion: 𝑣 = 𝑣Q 𝑒 -./0 ; 𝜏 = ; 𝛥𝑡R.ST = 2𝜏; 𝛥𝑥R.ST = 𝑣Q 𝛥𝑡R.ST OP;D > 3 Mathematics: V 𝑥 W = 𝑛𝑥 W-= V+ 4 Scratch paper 5 Scratch paper 6 Scratch paper 7 Scratch paper 8