SPH 4UI NAME______
Dynamics Unit Practice Test
Be sure to define all velocity and acceleration vectors for every question.
Part A: Short Answer (5 marks)
1. Use Newton’s Third Law to explain the motion of the following objects:
a. A rocket leaving a launch pad. (1 mark)
b. An airplane flying at constant velocity. (1 mark)
c. A runner’s foot pushing straight down on the ground. (1 mark)
2. A mass is suspended on a Newton spring scale in an elevator. What is the elevator doing when the scale shows the highest reading? (1 mark)
3. A skydiver jumps out of a plane and falls toward Earth’s surface. At some point in her fall, the force of air resistance is equal to the force of gravity acting on him. Describe the skydiver’s velocity at this point? (1 mark)
Part B: Calculations (45 marks)
1. You are in physics class operating a red remote controlled car around a circular path in the hallway. The car is undergoing centripetal acceleration of 3.38 m/s2. The radius of the car’s path is 1.25 m. Calculate the car’s speed. (3 marks)
Answer: 2.06 m/s
2. At Universal Studio’s Islands of Adventure, the Dr. Doom drop tower allows riders sit in a chair (with restraints, of course!) and closely experience free-fall as they go up and down a vertical tower. On the way down, the riders are almost free-falling.
a. On the way up, the riders initially experience a positive acceleration. Which is great at this point…apparent weight or true weight? (1 mark)
Answer: apparent
b. On the way down, which is greater…apparent weight or true weight? (1 mark)
Answer: true
c. On the way up, the riders accelerate from 0 m/s to 165 km/h in 3.0 s. The seat pushes up with a force of 1.52 x 103 N. The mass of the person is 61 kg. What is the person’s weight? (3 marks)
Answer: 5.9 x 102 N [down]
3. A 27 kg block is pushed from the top of an inclined ramp (40⁰ off of the horizontal) with an initial velocity of 1.8 m/s. The length of the ramp is 15 m long. If the coefficient of friction between these 2 surfaces is 0.50, calculate the speed of the block at the bottom of the ramp. (9 marks)
Answer: 8.9 m/s [down the slope]
4. A crate with mass 32.5 kg sits on a frictionless surface and is connected to a second crate by a string that passes over a pulley. The second crate has a mass of 40.0 kg. The pulley is frictionless and has no mass. The string also has no mass.
- Draw a FBD for each crate in the system. (4 marks)
- Determine the acceleration of the system of crates. (3 marks)
- Determine the magnitude of the tension in the string. (3 marks)
Answer: Ft = 176 N
5. Mrs. Meissner is in front of the class spinning a 2.3 kg bucket of water in a clockwise vertical loop with a radius of 1.0 m. (8 marks)
a. Sketch 4 sets of F.B.D.s, for the following 4 locations:
b. Calculate the minimum speed she needs to swing it so that it just barely maintains a circle.
Answer: 3.13 m/s
c. At that minimum speed, calculate the tension in the string at the top and the bottom.
Answer: Top Ft = 0 N
Bottom Ft = 45 N
6. You’re at the Canada’s Wonderland physics class trip and have decided to investigate the forces on the Nightmare ride. Nightmare is a rotating cylinder in which the rider stands in a cage. It starts by rotating clockwise. Draw two FBD for you as a rider on Nightmare while it’s in horizontal rotation: one from Mrs. Meissner’s perspective on the ground and another from your perspective on the ride. (4 marks)
7. Mrs. Meissner is driving on a curved road with a radius of 450 m in the horizontal plane. The curved road is banked so that cars can safely navigate the curve. Calculate the banking angle for the road that will allow a car travelling at 97 km/h to make it safely around the curve when the road is covered with black ice (i.e. assume no friction). (6 marks)
Answer: 9.3 degrees