Quiz 5.1

A 1.0 kg lump of clay is sliding to the right on a frictionless surface with speed 2 m/s . It collides head-on and sticks to a 0.5 kg metal sphere that is sliding to the left with speed 4 m/s . What is the kinetic energy of the combined objects after the collision?

• 6 J

• 4 J

• 2 J

• 0 J

Tags

NGSS.HS-PS2-2

A 12 kg box sliding on a horizontal floor has an initial speed of 4.0 m/s. The coefficient of friction between the box and the floor is 0.20. The box moves a distance of 4.0 m in 2.0 s. The magnitude of the change in momentum of the box during this time is most nearly

• 12 kg m/s

• 48 kg m/s

• 60 kg m/s

• 96 kg m/s

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A ball of mass 0.4 kg is initially at rest on the ground. It is kicked and leaves the kicker's foot with a speed of 5.0 m/s in a direction 60° above the horizontal. The magnitude of the impulse imparted by the ball to the foot is most nearly

• 1 Ns

• $\sqrt{3}$ Ns

• 2 Ns

• $\frac{2}{\sqrt{3}}$ Ns

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A cart of mass  $m$  is moving with negligible friction along a track with known speed  $v_1$  to the right. It collides with and sticks to a cart of mass  $4m$  moving with known speed  $v_2$  to the right. Which of the two principles, conservation of momentum and conservation of mechanical energy, must be applied to determine the final speed of the carts, and why? 

• Only conservation of momentum, because the momentum lost by one cart is gained by the other and there is only one unknown quantity.

• Both conservation of mechanical energy and conservation of momentum, because both principles apply in any collision

• Both conservation of mechanical energy and conservation of momentum, because neither cart changes direction.

• Either conservation of momentum or conservation of mechanical energy, because only one equation is required to solve for the one unknown variable

Tags

NGSS.HS-PS2-2

A dog of mass 10 kg sits on a skateboard of mass 2 kg that is initially traveling south at 2 m/s. The dog jumps off with a velocity of 1 m/s north relative to the ground. Which of the following is the best estimate of the velocity of the skateboard immediately after the dog has jumped?

• 1 m/s north

• 3 m/s south

• 7 m/s south

• 17 m/s south

Tags

NGSS.HS-PS2-2

An empty sled of mass  $M$  moves without friction across a frozen pond at speed  $v_0$  . Two objects are dropped vertically into the sled one at a time: first an object of mass  $m$  and then an object of mass  $2m$  . Afterward the sled moves with speed  $v_f$  . What would be the final speed of the sled if the objects were dropped into it in reverse order?

•  $\frac{v_f}{3}$  

•  $\frac{v_f}{2}$  

•  $v_f$  

•  $2v_f$  

Tags

NGSS.HS-PS2-2

Object X travels across a horizontal surface and collides with object Y. The velocity as a function of time for object X and object Y before, during, and after the collision is shown in the graph. Both objects have a mass of 2 kg . Which of the following correctly describes the momentum  $\overrightarrow{p}$  of the system and the kinetic energy  $K$  of the system?

• Momentum and Kinetic energy are conserved

• Only momentum is conserved

• Only Kinetic Energy is conserved

• Neither are conserved

Tags

NGSS.HS-PS2-2

Block X slides along a horizontal surface with speed  $v_x$  toward block Y that is initially at rest, as shown in Figure 1. After block X collides with block Y, the two blocks remain stuck together and travel at a velocity  $v_{xy}$ , as shown in Figure 2. Frictional forces are considered to be negligible. Which of the following claims is correct regarding the momentum of the system containing only block X and the system that contains block X and block Y?

• The system containing block X is an open system, and the system of both blocks is an open system.

• The system containing block X is an open system, and the system of both blocks is a closed system.

• The system containing block X is a closed system, and the system of both blocks is an open system.

• The system containing block X is a closed system, and the system of both blocks is a closed system.

Tags

NGSS.HS-PS2-2

Two identical spaceships are traveling in deep space, far from any planets or stars. The ships travel in the same direction, with the slower one directly behind the faster one. The ships are connected by a cable attached to a spool, so that the part of the cable outside the ships can be made longer or shorter as needed. The cable is used to bring the ships to the same speed for a transfer of cargo. The graph above shows the speed of the two ships during a 10 s interval.

Does at least one of the ships have its engine turned on during the time interval shown, and what evidence indicates so?

• Yes, because Ship 2 is speeding up.

• Yes, because the momentum of the two-rocket system increases.

• Yes, because an engine is needed to keep the system moving

• No, because the cable alone could be responsible for making Ship 1 slow down and Ship 2 speed up.

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A student must analyze data collected from an experiment in which a block of mass  $2M$  traveling with a speed  $v_0$  collides with a block of mass  $M$  that is initially at rest. After the collision, the two blocks stick together. Which of the following applications of the equation for the conservation of momentum represent the initial and final momentum of the system for a completely inelastic collision between the blocks? Justify your selection. Select two answers.

•  $2Mv_0=3Mv_f$  , because the blocks stick together after the collision

•  $3Mv_0=3Mv_f$  , because the blocks stick together after the collision

•  $2Mv_0=2Mv_f+Mv_f$  , because the blocks stick together after the collision

•  $2Mv_0=Mv_0+3Mv_f$  , because the blocks do not stick together after the collision

Tags

NGSS.HS-PS2-2