SPH4U - Review for Dynamics Test
Things to study for this first test:
Kinematics
- vectors
- speed
- velocity
- acceleration
- position
- displacement
- graphs
- free fall
- projectiles
- frames of reference
- relative velocities
Dynamics
- forces
- friction
- static and dynamic equilibrium
- Newton’s laws
- Free body diagrams
- Inclined plane questions
- Pulley questions
Circular Motion
- Uniform circular motion
- centripetal acceleration
- period
- frequency
· See pg 52, 98, and 138 in your text for the Chapter Summary for these Units. (Note: we did not cover rotating frames of reference)
· Consider trying the Self Quiz and Review Questions for this chapter in your text book.
· Look at your notes, at examples of questions we did in class, at the Tribal Challenge questions, and at the Review Questions to help you study.
**** Yes, you will be allowed a formula sheet *****
Practice Test – Dynamics
True/False
Indicate whether the sentence or statement is true or false.
____ 1. The normal force that acts on an object is never equal in magnitude and opposite in direction to the gravitational force that is acting on it.
____ 2. An object experiencing a net force of zero is either not moving or moving at a constant velocity.
____ 3. A projectile has both a horizontal and vertical component to its acceleration.
____ 4. For an object travelling with uniform circular motion there is no acceleration.
____ 5. A person sitting in an inertial reference frame can accurately observe Newton’s laws in action.
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____ 6. The free-body diagram of a block being pushed up a rough ramp is best represented by
a. / A / d. / Db. / B / e. / E
c. / C
____ 7. An object is pushed horizontally along a table and is accelerating forward. What can correctly be said about the forces acting on the object?
a. / The force(s) acting forward is/are greater than the force(s) acting backward.b. / The sum of all forces has a value directed backward.
c. / The sum of all forces is zero.
d. / The forces acting on the object can be said to be “balanced.”
e. / Newton’s first law best summarizes the effect of the forces acting on the object.
____ 8. A 50 g wagon is accelerated left at 6 m/s2. What is the magnitude of the net force?
a. / 30 N [left] / d. / 0.3 Nb. / 0.3 N [left] / e. / 8.3 N
c. / 300 N [left]
____ 9. A 2.8-kg cart is pulled with a force of 10 N at an angle of 50° above the horizontal. If a kinetic friction force of 3 N acts against the motion, the magnitude of the cart’s acceleration along the horizontal surface will be
a. / 3.57 m/s2 / d. / 1.07 m/s2b. / 3.427 m/s2 / e. / 9.5 m/s2
c. / 1.22 m/s2
____ 10. A 5.0-kg object is pulled horizontally by a force of 16 N along the floor where the coefficient of kinetic friction is 0.3. What is the magnitude of the object’s acceleration?
a. / 0.257 m/s2 / d. / 1.2 m/s2b. / 2.94 m/s2 / e. / 6.4 m/s2
c. / 3.2 m/s2
____ 11. The slope of a line drawn tangent to a curved position-time graph represents
a. / displacement / d. / accelerationb. / instantaneous velocity / e. / distance
c. / average velocity
____ 12. How long does it take a car to slow down from a speed of 54 km/h to 32 km/h over a distance of 65 m? Answer in seconds.
a. / 21 / d. / 2.7b. / 5.9 / e. / 1.5
c. / 5.4
____ 13. An object is thrown vertically downward at 5 m/s. How long will the object take to hit the ground 20 m below?
a. / 2.6 s / d. / 3.8 sb. / 1.6 s / e. / 4.2 s
c. / 3.1 s
____ 14. A toy car is moving at 13 cm/s when it begins accelerating at 1.4 cm/s2. If the acceleration is uniform, what is the speed of the car after it has travelled a distance of 27 cm?
a. / 2.4 ´ 102 cm/s / d. / 16 cm/sb. / 93 cm/s / e. / 1.0 ´ 101 cm/s
c. / 62 cm/s
____ 15 For an object travelling with “uniform circular motion,” its acceleration is
a. / zero because the speed is constantb. / directed tangent to the circle
c. / directed toward the centre of the circle
d. / changing in magnitude depending on its position in the circle
e. / directed outward from the centre of the circle
____ 16. An object moves with a speed of 3 m/s in a circle of radius 4 m. The magnitude of the centripetal acceleration is
a. / 0.75 m/s2 / d. / 2.25 m/s2b. / 12 m/s2 / e. / 1 m/s2
c. / 5.3 m/s2
____ 17. A child whirls a ball around in circles on the end of a 30 cm long string at a frequency of 3 Hz. What is the ball’s centripetal acceleration?
a. / 11 m/s2 / d. / 1131 m/s2b. / 36 m/s2 / e. / 0.35 m/s2
c. / 3553 m/s2
Short Answer
18. Draw the free body diagram of a skier who is skiing down a snow-covered hill (include friction)
19. Draw the free body diagram of a football that is being thrown through the air
Problems
20. A ball on a string, moving in a horizontal circle of radius 2.0m, undergoes a centripetal acceleration of magnitude 15 m/s2. What is the speed of the ball?
21. A rollercoaster has a circular loop with a radius of 15 meters. What is the minimum speed required by the cart at the top of this loop?
22. A plane is travelling with an air speed of 300 km/s [35º W of N] relative to the wind . A wind is blowing at 75 km/h [E] relative to the ground. Determine the velocity of the plane relative to the ground.
23. A boat travelling at 30 m/s [35º E of N] takes 20 seconds to change its velocity to 25m/s [25º E of S]. What is the average acceleration over this time interval?
24. A 12.0-kg box is pushed along a horizontal surface by a 24-N force as illustrated in the diagram. The frictional force (kinetic) acting on the object is 6.0 N.
(a) What is the acceleration of the object?
(b) Calculate the value of the normal force acting on the object.
(c) If the 12.0-kg object then runs into a 4.0-kg object that increases the overall friction by 3.0 N, what is the new acceleration?
(d) What force does the 4.0-kg object exert on the 12.0-kg object when the two are moving together?
25. A shell is fired from a cliff that is 36 m above a horizontal plane. The muzzle speed of the shell is 80.0 m/s and it is fired at an elevation of 25° above the horizontal.
(a) Determine the horizontal range of the shell.
(b) Determine the velocity of the shell as it strikes the ground.
26. Two masses, 4.0 kg and 6.0 kg, are connected by a “massless” rope over a “frictionless” pulley as pictured in the diagram. The ramp is inclined at 30.0º and the coefficient of kinetic friction on the ramp is 0.18.
(a) Draw free-body diagrams of both masses.
(b) Determine the acceleration of the system once it begins to slide.
(c) Determine the tension in the rope.
(d) If the rope breaks when the 4.0-kg mass is 3.0 m from the bottom of the ramp, how long will it take for the mass to slide all the way down? Include a new free-body diagram and assume the sliding mass starts from rest.
27. A ball is thrown vertically upward from a window that is 3.6 m above the ground. Its initial speed is 2.8 m/s.
(a) With what speed does the ball hit the ground?
(b) How long after the first ball is thrown should a second ball be simply dropped from the same window so that both balls hit the ground at the same time?
28. The graph below represents the motion of an object over a recorded time interval. Using methods of graphical analysis wherever possible, determine
(a) the object’s displacement relative to its starting position at t = 6.0 s.
(b) the object’s average velocity between t = 0.0 s and t = 6.0 s.
(c) the object’s average speed between t = 0.0 s and t = 6.0 s.
(d) Including t = 0.0 s, how many times during the entire recorded time interval is the object at its starting position?
(e) During which interval is the object’s acceleration the greatest? What is the value of the acceleration during this interval?
(f) Plot the corresponding position-time graph.
(g) Plot the corresponding acceleration-time graph.