Chapter 4
Review
Chapter 4 Review
2) While an object is in projectile motion (with upward being positive) with no airresistanceA) thehorizontal component of its velocity remains constant and the horizontalcomponent ofits acceleration is equal to -g.B) the horizontal component of its velocity remains constant and the vertical componentof itsacceleration is equal to–gC) the horizontal component of its velocity remains constant and the vertical componentof itsacceleration is equal to zero.D) the vertical component of both its velocity and its acceleration remain constant.E) the vertical component of its velocity remains constant and the vertical component ofits accelerationis equal to -g.
Chapter 4 Review
2) While an object is in projectile motion (with upward being positive) with no airresistanceA) thehorizontal component of its velocity remains constant and the horizontalcomponent ofits acceleration is equal to -g.B) the horizontal component of its velocity remains constant and the vertical componentof itsacceleration is equal to–gC) the horizontal component of its velocity remains constant and the vertical componentof itsacceleration is equal to zero.D) the vertical component of both its velocity and its acceleration remain constant.E) the vertical component of its velocity remains constant and the vertical component ofits accelerationis equal to -g.Ans: B
Chapter 4 Review
3) For general projectile motion, when the projectile is at the highest point of itstrajectoryitsacceleration is zero.B) its velocity is perpendicular to the acceleration.C) its velocity and acceleration are both zero.D) the horizontal component of its velocity is zero.E) the horizontal and vertical components of its velocity are zero.
Chapter 4 Review
3) For general projectile motion, when the projectile is at the highest point of itstrajectoryitsacceleration is zero.B) its velocity is perpendicular to the acceleration.C) its velocity and acceleration are both zero.D) the horizontal component of its velocity is zero.E)the horizontal and vertical components of its velocity are zero.Ans: B
Chapter 4 Review
4) Alice and Tom dive from an overhang into the lake below. Tom simply drops straightdown fromthe edge, but Alice takes a running start and jumps with an initial horizontal velocityof 25m/s. Neither person experiences any significant air resistance. Just as they reach thelake belowA) the speed of Alice is larger than that of Tom.B) the splashdown speed of Alice is larger than that of Tom.C) they will both have the same speed.D) the speed of Tom will always be 9.8 m/s larger than that of Alice.E) the speed of Alice will always be 25 m/s larger than that of Tom.
Chapter 4 Review
4) Alice and Tom dive from an overhang into the lake below. Tom simply drops straightdown fromthe edge, but Alice takes a running start and jumps with an initial horizontal velocityof 25m/s. Neither person experiences any significant air resistance. Just as they reach thelake belowA) the speed of Alice is larger than that of Tom.B) the splashdown speed of Alice is larger than that of Tom.C) they will both have the same speed.D) the speed of Tom will always be 9.8 m/s larger than that of Alice.E) the speed of Alice will always be 25 m/s larger than that of Tom.ANS:A
Chapter 4 Review
5) Alice and Tom dive from an overhang into the lake below. Tom simply drops straightdown fromthe edge, but Alice takes a running start and jumps with an initial horizontal velocity of25 m/s. Neither person experiences any significant air resistance. Compare the time ittakes eachof them to reach the lake below.A) Alice reaches the surface of the lake first.B) Tom reaches the surface of the lake first.C) Alice and Tom will reach the surface of the lake at the same time.
Chapter 4 Review
5) Alice and Tom dive from an overhang into the lake below. Tom simply drops straightdown fromthe edge, but Alice takes a running start and jumps with an initial horizontal velocity of25 m/s. Neither person experiences any significant air resistance. Compare the time ittakes eachof them to reach the lake below.A) Alice reaches the surface of the lake first.B) Tom reaches the surface of the lake first.C) Alice and Tom will reach the surface of the lake at the same time.ANS: C
Chapter 4 Review
7) A monkey is sitting at the top of a tree 20 m above ground level. A person standing onthe groundwants to feed the monkey. He uses a bow and arrow to launch the food to themonkey. Ifthe person knows that the monkey is going to drop from the tree at the same instant thatthe personlaunches the food, how should the person aim the arrow containing the food?Air resistanceis small enough to be ignored.A) He should aim it at the monkey.B) He should aim it below the monkey.C) He should aim it above the monkey.
Chapter 4 Review
7) A monkey is sitting at the top of a tree 20 m above ground level. A person standing onthe groundwants to feed the monkey. He uses a bow and arrow to launch the food to themonkey. Ifthe person knows that the monkey is going to drop from the tree at the same instant thatthe personlaunches the food, how should the person aim the arrow containing the food?Air resistanceis small enough to be ignored.A) He should aim it at the monkey.B) He should aim it below the monkey.C) He should aim it above the monkey.ANS: A
Chapter 4 Review
9) For an object in uniform circular motion, its velocity and acceleration vectors are alwaysperpendicular to each other at every point in the path.A) TrueB) False
Chapter 4 Review
9) For an object in uniform circular motion, its velocity and acceleration vectors are alwaysperpendicular to each other at every point in the path.A) TrueB)FalseANS: A
Chapter 4 Review
10) If an object travels at a constant speed in a circular path, the acceleration of the objectisA) larger in magnitude the smaller the radius of the circle.B) in the same direction as the velocity of the object.C) smaller in magnitude the smaller the radius of the circle.D) in the opposite direction of the velocity of the object.E) zero.
Chapter 4 Review
10) If an object travels at a constant speed in a circular path, the acceleration of the objectisA) larger in magnitude the smaller the radius of the circle.B) in the same direction as the velocity of the object.C) smaller in magnitude the smaller the radius of the circle.D) in the opposite direction of the velocity of the object.E) zero.Answer: A
Chapter 4 Review
6) A hockey puck slides off the edge of a table at pointAwith an initial velocity of 20.0 m/sand experiencesno air resistance. The height of the tabletop above the ground is 2.00 m.Whatis the speed (not the velocity) of the puck just before it touches the ground?(b) What is the distance between pointAand the point where the puck hits the ground?
Chapter 4 Review
6) A hockey puck slides off the edge of a table at pointAwith an initial velocity of 20.0 m/sand experiencesno air resistance. The height of the tabletop above the ground is 2.00 m.Whatis the speed (not the velocity) of the puck just before it touches the ground?ANS: 21.0 m/a(b) What is the distance between pointAand the point where the puck hits the ground?ANS: 12.9 m
Chapter 4 Review
7) A hockey puck slides off the edge of a table with an initial velocity of 28.0 m/s.and experiencesno air resistance. The height of the tabletop above the ground is 2.00 m. What isthe angle below the horizontal of the velocity of the puck just before it hits the ground?
Chapter 4 Review
7) A hockey puck slides off the edge of a table with an initial velocity of 28.0 m/s.and experiencesno air resistance. The height of the tabletop above the ground is 2.00 m. What isthe angle below the horizontal of the velocity of the puck just before it hits the ground?ANS: 12.6 °
Chapter 4 Review
8) A boy throws a rock with an initial velocity of 2.15 m/s at 30.0° above the horizontal. Ifair resistanceis negligible, how long does it take for the rock to reach the maximum height ofits trajectory?
Chapter 4 Review
8) A boy throws a rock with an initial velocity of 2.15 m/s at 30.0° above the horizontal. Ifair resistanceis negligible, how long does it take for the rock to reach the maximum height ofits trajectory?ANS: 0.110 s
Chapter 4 Review
10) A catapult is tested by Roman legionnaires. They tabulate the results in a papyrus and2000 yearslater the archaeological team reads (distances translated into modern units):Range = 0.20 km; angle of launch = π/4; landing height = launch height. What is theinitial velocityof launch of the boulders if air resistance is negligible?
Chapter 4 Review
10) A catapult is tested by Roman legionnaires. They tabulate the results in a papyrus and2000 yearslater the archaeological team reads (distances translated into modern units):Range = 0.20 km; angle of launch = π/4; landing height = launch height. What is theinitial velocityof launch of the boulders if air resistance is negligible?ANS 44.0 m/s
Chapter 4 Review
19) A hiker throws a stone from the upper edge of a vertical cliff. Thestone'sinitial velocity is25.0 m/sdirected at 40.0° with the face of the cliff, as shown in the figure. The stone hits theground 3.75s after being thrown and feels no appreciable air resistance as it falls.(a) What is the height of the cliff?(b) How far from the foot of the cliff does the stone land?(c)How fast is the stone moving just before it hits the ground?
Chapter 4 Review
19) A hiker throws a stone from the upper edge of a vertical cliff. Thestone'sinitial velocity is25.0 m/sdirected at 40.0° with the face of the cliff, as shown in the figure. The stone hits theground 3.75s after being thrown and feels no appreciable air resistance as it falls.(a) What is the height of the cliff?(b) How far from the foot of the cliff does the stone land?(c)How fast is the stone moving just before it hits the ground?Answer: (a) 141 m (b) 60.3 m (c) 58.2 m/s
Chapter 4 Review
24) A plane has an eastward heading at a speed of 156 m/s (relative to the air). A 20.0 m/s windis blowingsouthward while the plane is flying. The velocity of the plane relative to the groundis:
Chapter 4 Review
24) A plane has an eastward heading at a speed of 156 m/s (relative to the air). A 20.0 m/s windis blowingsouthward while the plane is flying. The velocity of the plane relative to the groundis:Ans:157 m/s at an angle 7.31° south of east.
Chapter 4 Review
32) An electrical motor spins at a constant 2857.0 rev/min. If the armature radius is 2.685 cm,what isthe acceleration of the outer edge of the armature?
Chapter 4 Review
32) An electrical motor spins at a constant 2857.0 rev/min. If the armature radius is 2.685 cm,what isthe acceleration of the outer edge of the armature?ANS:2403m/s2
Chapter 4 Review
During a rainstorm, raindrops are observed to be striking the ground at an angle of 35 degrees with the vertical. The wind speed is 4.5 m/s. Assuming that the horizontal velocity component of the raindrops is the same as the speed of the air, what is the vertical velocitycomponentof the raindrops? What is their speed?
Chapter 4 Review
During a rainstorm, raindrops are observed to be striking the ground at an angle of 35 degrees with the vertical. The wind speed is 4.5 m/s. Assuming that the horizontal velocity component of the raindrops is the same as the speed of the air, what is the vertical velocitycomponentof the raindrops? What is their speed?Ans: 6.43 m/s down7.84m/s5.52
Chapter 4 Review
A rowboat is pointing perpendicular to the bank of a river. The rower can propel the boat with a speed of 3.0 m/s with respect to the water. The river has a current of 4.0 m/s. If the river is100.m wide, determine how far downstream of the launch point the rowboat is when it reaches the opposite bank.
Chapter 4 Review
A rowboat is pointing perpendicular to the bank of a river. The rower can propel the boat with a speed of 3.0 m/s with respect to the water. The river has a current of 4.0 m/s. If the river is100.m wide, determine how far downstream of the launch point the rowboat is when it reaches the opposite bank.ANS:130m5.53
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