Center of Mass + Review

Where is the center of mass of this image? Just look!

• at 20 mark

• at 42.5 mark

• at 50 mark

• at 100 mark

If m1 = 3 kg, m2 = 4 kg, and m3 = 2 kg, find the center of mass of the system as an ordered pair (x, y). Type in your answer using whole numbers only. Signs matter!

(a)  

A 0.15 kg baseball travelling in a horizontal direction with a speed of 20 m/s hits a bat and is popped straight up with a speed of 33 m/s. What is the average force exerted on popping the ball straight up for 0.005 s?

• 830 N

• 780 N

• 650 N

• 390 N

Tags

NGSS.HS-PS2-1

A 0.15 kg baseball travelling in a horizontal direction with a speed of 20 m/s hits a bat and is popped straight up with a speed of 33 m/s. What is the impulse caused by hitting the ball?

• 5.60 kgm/s

• 6.25 kgm/s

• 4.95 kgm/s

• None of the choices

Tags

NGSS.HS-PS2-2

A car of mass 2 542 kg stopped at a parking lot is bumped from the rear by a bicycle of 15 kg. If the bicycle is moving at 49 m/s before the collision, what is the velocity of the car and the bicycle after the collision?

• 0.13 m/s

• 0.95 m/s

• 0.29 m/s

• 0.57 m/s

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A car of mass 2 500 kg stopped at a traffic light is struck from the rear by a 1 200 kg car. If the smaller car was moving at 20 m/s before the collision, what is the velocity of the entangled cars before the collision?

• 7.93 m/s

• 8.09 m/s

• 6.49 m/s

• 8.63 m/s

Tags

NGSS.HS-PS2-2

A system consists of two particles at different locations near the origin. Particle 1 has a mass of 7.89 kg and is located on the x-axis at x = –5.0 m while Particle 2 has 9.75 kg mass and is located at y = +8.0 m. What is the center of the mass of the two particles at x – axis?

• x = -1.68 mi

• x = -2.24 mi

• x = 2.18 mi

• x = 4.82 mi

A system consists of two particles at different locations near the origin. Particle 1 has a mass of 7.89 kg and is located on the x-axis at x = –5.0 m while Particle 2 has 9.75 kg mass and is located at y = +8.0 m. What is the center of the mass of the two particles at y – axis?

• y = 4.42 mj

• y = - 3.21 mj

• y = 5.03 mj

• y = - 1.25 mj

Suppose a cart has a kinetic energy of 0.5 J. If you add enough mass to double the mass and make the cart go three times as fast, its kinetic energy is now ---.

• 6 J

• 3 J

• 18 J

• 9 J

Answer explanation

KE = ½mv²

Rule of ones:

1 in for m, 3 in for v

1·3² = 9×

9×0.5 = 0.45

Tags

NGSS.HS-PS3-1

What is the displacement from 2 to 10 seconds?

• 64 km

• 100 m

• 64m 

• 32 m 

Tags

NGSS.MS-PS3-1