Q2.2.a An object is moving in the +x direction. 1) A only 2) B only Which of the following 3) C only statements about the net force 4) A and B acting on the object could be 5) B and C true? 6) A and C 7) A, B, and C A. The net force is in the +x direction B. The net force is in the –x direction C. The net force is zero
Q2.2.b Cart A moves to the left at Which cart(s) nearly constant speed. experience a net force to the left? Cart B moves to the left, gradually speeding up. 1) A only 2) B only Cart C moves to the left, 3) C only gradually slowing down. 4) A and B 5) B and C 6) A and C 7) A, B, and C
Q2.3.a: The x-component of What can you conclude momentum of an object is about the x-component of found to increase with the net force acting on the time: object? t = 0 s px = 30 kg m/s t = 1 s px = 40 kg m/s 1) Fnet,x = 0 t = 2 s px = 50 kg m/s 2) Fnet,x is constant t = 3 s px = 60 kg m/s 3) Fnet,x is increasing with time 4) Not enough information is given to determine which is true. Q2.3.b
A hockey puck is sliding along 1) < 10, 0, 11 > kg· m/s the ice with nearly constant 2) < 0, 0, 6 > kg· m/s momentum 3) 14.86 kg· m/s < 10, 0, 5 > kg m/s when it is 4) < 16, 0, 11 > kg· m/s suddenly struck by a hockey 5) < 0, 0, 30 > kg· m/s stick with a force < 0, 0, 2000 > N that lasts for only 3 milliseconds (3e-3 s).
What is the new (vector) momentum of the puck?
Q2.3.c: You push a book across a 1) A net force is necessary to table. In order to keep keep an object moving. the book moving with 2) To make the net force on constant momentum, you the book zero, you must have to keep pushing push with a force equal and with a constant force. opposite to the friction force on the book. Which statement explains 3) The force you exert must this? be slightly larger than the friction force.
Q2.3.d:
Inside a spaceship in outer 1) < -28, 23, 0 > kg· space there is a small steel m/s ball. At a particular instant, the 2) < 12, -7, 0 > kg· m/s ball has momentum < -8, 3, 0 > 3) 36.2 kg· m/s kg· m/s and is pulled by a 4) < 32, -17, 0 > kg· string, which exerts a force < m/s 20, -10, 0 > N on the ball. 5) < 40, -20, 0 > kg· What is the ball’s (vector) m/s momentum 2 seconds later?
Q2.5.a:
A ball is initially on the ground, 1) px and you kick it with initial 2) py velocity < 3,7,0> m/s. At this 3) p speed air resistance is z negligible. Assume the usual 4) px & py coordinate system. 5) py & pz
5) pz & px Which components of the ball's momentum will change in the 7) px, py, & pz next half second? Q2.5.b: The mass of the ball is 500 g, 1) < 0, 2.45, 0 > N*s and its initial velocity is < 2) < 0, –2.45, 0 > N*s 3,7,0> m/s. What is the net 3) < 0, 9.8, 0 > N*s impulse acting on the ball 4) < 0, –9.8, 0 > N*s during the next 0.5 seconds 5) < 0, 4.9, 0 > N*s after you kicked it? 6) < 0, –4.9, 0 > N*s The initial momentum of the ball was < 1.5, 3.5, 0 > kg*m/s. The final momentum of the ball is < 1.5, 1.05, 0 > kg*m/s.
Therefore... Q2.5.c: Which graph correctly shows py for the ball during this 0.5 s?
1 2 3 Q2.5.d: Initially the velocity of the ball 1) 2.10 m/s is 2) 4.55 m/s < 3 , 7 ,0 > m/s. After 0.5 s, the 3) 4.90 m/s ball's velocity is < 3, 2.1, 0 > 4) 7.00 m/s m/s. 5) 9.10 m/s
What is the best choice for the y-component of the ball's average velocity during this interval?
Q2.6.a A student is running 1) 0.1 m/s very fast. What is the 2) 1 m/s student’s approximate 3) 10 m/s speed? (Think about 4) 100 m/s what you know about 5) 1000 m/s track and field events.)
Q2.6.b Two running students collide head-on One student exerts a force of 1) < F, 0, 0 > magnitude F on the other 2) < 2F, 0, 0 > student. Suppose we choose 3) < 0, 0, 0 > BOTH students as the “system” to which to apply the momentum principle. What is the net force acting on this system? Q2.6.c Approximately what is the time 1) 0.001 s interval t from just before the 2) 0.01 s students make contact to just 3) 0.1 s after? 4) 1 s 5) 10 s Q2.9.a When a ping pong ball 1) The momentum of the collides with a bowling bowling ball does not change. ball, why is the effect 2) The change in the bowling on the ping pong ball ball’s momentum is less than more noticeable than the change in the ping pong the effect on the ball’s momentum. bowling ball? 3) The change in the bowling ball’s velocity is less than the change in the ping pong ball’s velocity. Q2.9.b A bowling ball is initially at In this time interval, what rest. A ping pong ball moving is the sign of pz for the in the +z direction hits the system consisting of both bowling ball, and bounces off balls? it, traveling back in the –z direction. 1) positive 2) negative Consider a time interval t 3) zero – no change in pz from slightly before to slightly after the collision.
Q2.9.c A bullet of mass m traveling What should you choose as horizontally at a very high the speed v system? embeds itself in a block of mass M 1) the bullet that is sitting at rest on a very slippery sheet of ice. 2) the block
You want to find the speed of 3) the bullet and the block the block just after the bullet embeds itself in the block.
Q2.9.d: A bullet of mass m 1) v traveling horizontally at a very m 2) v high speed v M m embeds itself in a block of mass M m 3) v M m that is sitting at rest on a very m slippery sheet of ice. 4) v M What is the speed of the block m 5) v just after the bullet embeds M m itself in the block?
Q2.9.e: A space satellite of mass 500 1) < –5100, 0, –400 > m/s kg has velocity < 12, 0, –8 > 2) < –10.2, 0, –0.8 > m/s m/s just before being struck by a rock of mass 3) < 10.2, 0, 0.8 > m/s 3 kg with velocity < –3000, 0, 4) < –3688, 0, 1191 > m/s 900 > m/s. 5) < 3688, 0, –1192 > m/s
After the collision the rock’s velocity is < 700, 0, –300 > m/s. Now what is the velocity of the space satellite?