25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt. 25 pt. 5 pt. 10 pt. 15 pt. 20 pt.

1-5 How do you calculate the momentum of an object?

1-5A How do you calculate the momentum of an object? Momentum = Mass x Velocity

1-10 True or False? Momentum is a vector quantity.

1-10A True or False? Momentum is a vector quantity. True

1-15 What is the momentum of a 520 g object moving at a velocity of 14 m / s ?

1-15A What is the momentum of a 520 g object moving at a velocity of 14 m / s ? Momentum = Mass x Velocity p = mv = (0.520 kg)(14 m / s ) p = 7.28 kg m / s

1-20 A)a.22-caliber bullet fired from a rifle B)a bus speeding along a highway C)a sprinter running the 100-yard dash D)the Earth in its orbit E)not enough info to answer Which of the following objects has the greatest Momentum?

1-20A A)a.22-caliber bullet fired from a rifle B)a bus speeding along a highway C)a sprinter running the 100-yard dash D)the Earth in its orbit E)not enough info to answer Which of the following objects has the greatest Momentum?

1-25 What is the total momentum of the following situation? Assume there is no friction. 2 kg 1.5 m / s 0.8 m / s 4 kg

1-25A What is the total momentum of the following situation? Assume there is no friction. Momentum of LH-cart = (2 kg)(1.5 m / s ) = + 3 kg m / s Momentum of RH-cart = (4 kg)(- 0.8 m / s ) = kg m / s Total Momentum = + 3 kg m / s – 3.2 kg m / s p Tot = -0.2 kg m / s (to the left) 2 kg 1.5 m / s 0.8 m / s 4 kg

2-5 An impulse is equal to which of the following? A) force times distance B) force of impact C) change in kinetic energy D) change in momentum E) none of these

2-5A An impulse is equal to which of the following? A) force times distance B) force of impact C) change in kinetic energy D) change in momentum E) none of these

2-10 If a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact?

2-10A If a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact? Increase the time of impact

2-15 What is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds?

2-15A What is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds? Change in momentum = impulse = F t F t = (75 N)(0.18 s) F t = 13.5 N s

2-20 A 10kg bowling ball is dropped 5m onto the floor, and it bounces perfectly elastically. If the contact time is 1/100 sec, what is the force on the ball?

2-20A A 10kg bowling ball is dropped 5m onto the floor, and it bounces perfectly elastically. If the contact time is 1/100 sec, what is the force on the ball? (Kinematics gives: v i = 10 m / s, v f = -10 m / s ) I = Ft = m  v F = (10kg)(-10 m / s - 10 m / s )*100 s F = -20,000 N (upward)

2-25 A 1,000 kg rocket is launched horizontally from rest to a speed of 2500 m/sec in a time of 2.5 minutes. What was the average force exerted on the rocket?

2-25A A 1,000 kg rocket is launched horizontally from rest to a speed of 2500 m/sec in a time of 2.5 minutes. What was the average force exerted on the rocket? Change in momentum = Impulse m  v = F t ==> F = m  v / t F = (1000 kg)(2500 m / s - 0 m / s )/(150 s) F = 16,667 Newtons

3-5 True or False? Momentum is conserved in all kinds of collisions.

3-5A True or False? Momentum is conserved in all kinds of collisions. True

3-10 Which kind of collision conserves both momentum and kinetic energy? A) elastic B) inelastic C) both D) neither

3-10A Which kind of collision conserves both momentum and kinetic energy? A) elastic B) inelastic C) both D) neither

3-15 Why is it safer to stop an out-of- control car by running into a pond versus hitting a concrete wall?

3-15A Why is it safer to stop an out-of- control car by running into a pond versus hitting a concrete wall? By running into the pond, the time it takes the car to slow down to a stop is lengthened. Therefore the stopping force is decreased.

3-20 Why is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)?

3-20A Why is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)? A bouncing collision is more damaging because the change in velocity, and therefore the change in momentum, is greater. This leads to a larger force.

3-25 A 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is sec, what was the force of impact on the ball?

3-25A A 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is sec, what was the force of impact on the ball? Impulse = Change in Momentum F t = m  v ==> F = m  v / t F = (0.25 kg)(-45 m / s )/(0.078 s) F = Newtons

4-5 When an asteroid collides with the Moon, the Moon drastically changes the momentum of the asteroid. By how much does the Moon change its momentum?

4-5A When an asteroid collides with the Moon, the Moon drastically changes the momentum of the asteroid. By how much does the Moon change its momentum? Precisely the same amount

4-10 A firecracker is sitting on the tip of a stick when it is lit. After the explosion, what is the total momentum of the pieces flying away?

4-10A A firecracker is sitting on the tip of a stick when it is lit. After the explosion, what is the total momentum of the pieces flying away? Zero!!! …because the momentum of the firecracker before the explosion was zero, and momentum must be conserved.

4-15 A hover puck slides along at 5m/s. It glances off another (elastically) and travels at 4.92m/s at 10 o. The stationary puck goes down and to the right. How fast does this 2 nd puck travel, and at what direction? 10 o

4-15A A hover puck slides along at 5m/s. It glances off another (elastically) and travels at 4.92m/s at 10 o. The stationary puck goes down and to the right. How fast does this 2 nd puck travel, and at what direction? KE 1 = KE 1 ' + KE 2 ' ½ mv 1 2 = ½ mv 1' 2 + ½ mv 2' 2 v 2' = 0.89 m / s It travels at 80 o below the original path (90 o from the other puck).

4-20 Two billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision? Bonk! #1 #2 A B C

4-20A Two billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision? Bonk! #1 A B C #2

4-25 Type Question Here

Momentum of LH-cart = (3 kg)(2.5 m / s ) = +7.5 kg m / s Momentum of RH-cart = (2 kg)(-1.8 m / s ) = -3.6 kg m / s Total Momentum = +3.9 kg m / s After collision ==> 3.9 kg m / s = (5 kg)v v = (3.9 kg m / s ) / (5 kg) = m/sec 4-25A 3 kg 2.5 m / s 1.8 m / s 2 kg

5-5 Name the Seven Dwarves (in alphabetic order)

5-5A Bashful Doc Dopey Grumpy Happy Sleepy Sneezy

5-10 Name the actor and movie that produced this famous quote: “Boards don’t hit back.”

5-10A Bruce Lee, in Enter the Dragon

5-15 The word “Hamster” means what in German? A) Bacon Mix B) Hoarder C) Rodent D) Nocturnal

5-15A The word “Hamster” means what in German? A) Bacon Mix B) Hoarder C) Rodent D) Nocturnal

5-20 How many triangles are there in this figure?

5-20A 35

What California gold-rush entrepreneur used his knowledge of bouncing collisions to design a nearly 90% efficient water wheel?

5-25A Lester A. Pelton, inventor of the Pelton water wheel

Daily Double Two carts collide and stick together as shown above. What is the velocity of the carts after they’ve collided? Assume there is no friction with the ground. 3 kg 2.5 m / s 1.8 m / s 2 kg