A 2 500-kg truck moving at 10.00 m/s strikes a car waiting at a traffic light, h

Question

A 2 500-kg truck moving at 10.00 m/s strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at 7.00 m/s. What was the mass of the struck car? 1 730 kg 1 550 kg 1 200 kg 1 070 kg 967 kg Point masses are distributed in the x, y-plane as follows: 6.0 kg at (0.0, 0.0)m, 4.0 kg at (2.0, 0.0)m, and 5.0 kg at (2.0, 3.0)m. What is the x-coordinate of the center of mass of this system of masses? 18 m 2.0 m 1.2 m 1.0 m 0.96 m A wheel rotating about a fixed axis with a constant angular acceleration of 2.0 rad/s^2 turns through 2.4 revolutions during a 2.0-s time interval. What is the angular velocity at the end of this time interval? 9.5 rad/s 9.7 rad/s 9.3 rad/s 9.1 rad/s 8.8 rad/s

Explanation / Answer

4)

m2 = 1071.43kg
from m1v1=v2(m1+m2)

so ans is (d)

5)

Let the co-ordinates of the given mass be X and Y and the co-ordinates of centre of mass be x-cm and y-cm.

so, x-cm = summation of product of all the masses and x co-ordinate of respective masses


x-cm = (6 x 0) + (4 x 2) + (5 x 2)

x –cm = 18cm

So ans is (A)

6)

The wheel is rotating with an angular acceleration of 2 rad/ s, and it turns 2.4 revolution, let's find the value of theta :

1 rev = 2pi, then 2.4 rev = 4.8pi rad

theta = 4.8 rad

time = 2 seconds

then we can use : theta = Wo*t + a*t^2 / 2

Wo = initial angular velocity

4.8pi = wo.2 + 2*4 /2

4.8pi = 2wo + 4

wo = 5.53 rad /s

Now, to find the final angular velocity, let's use :

Wf = Wo + at

Wf = 5.53 + 2*2 = 9.53 rad / s

So ans is (A)

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