# IGNOU BPHE-101 SOLVED ASSIGNMENT 2019

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**IGNOU BPHE-101 SOLVED ASSIGNMENT 2019**

**Tutor Marked Assignment**

**ELEMENTARY MECHANICS**

**Course Code: BPHE-101/PHE-01**

**Assignment Code: BPHE-101/PHE-01/TMA/2019**

**1. An object of mass 20 kg is pulled up with a force of 150 N on an inclined plane for a**

**distance of 3.0 m. The plane makes an angle of 30º with the horizontal and the**

**coefficient of kinetic friction between the object and the plane is 0.3. Draw the free**

**body diagram and calculate the work done by each force. (Take g = 10 ms−2 ****) (10)**

**2. A ball of mass 0.5 kg collides with a wall at a speed of 15.0 ms−1 and bounces back with**

**a speed of 12.5 ms−1****. If the average force exerted by the ball is 1100 N calculate the**

**impulse and the time for which the collision lasted. (10)**

**3. A truck of mass 2000 kg encounters a constant frictional force of 800 N as it moves on**

**a straight road. The speed of the truck increases from 20 ms−1**

**to 30 ms−1**

**as it covers a**

**distance of 400 m. What is the thrust generated by the truck’s engine? (10)**

**4. A cylindrical drum has a radius of 0.45 m and is initially at rest. It is then given an**

**angular acceleration of 0.40 rad s−2**

**. At time t = 8.0 s calculate (i) the angular speed of**

**the drum, (ii) the centripetal acceleration of a point on the rim of the drum, (iii) the**

**tangential acceleration at that point, and (iv) the resultant acceleration at that point. (10)**

**5. A 1000 kg truck is parked on a bridge 100 m long at a distance of 25 m from one end of**

**the bridge. The mass of the bridge is 200 kg m−1**

**. Calculate the reaction forces at the**

**supports at the two ends of the bridge. (Take g = 10 ms−2****) (10)**

**6. The mass (in kg), position coordinates (in m) and velocity (in m s−1 ****) of a system of**

**three particles A, B and C are as follows:**

**Particle Mass Position Velocity**

**A 2.0 kg (0, 0) 0**

**r**

**B 1.0 kg (2, 0) 4.0 j**

**ˆ**

**C 3.0 kg (1, 1) 2.0 i**

**ˆ**

**Calculate the coordinates of the centre of mass of the system and its momentum. (10)**

**7. A wheel having a moment of inertia of 1.0 kg m2**

**, is rotating about an axis through its**

**centre and perpendicular to its plane, at a speed of 30 rad s−1**

**. Due to friction on its axis,**

**it comes to rest in 10 minutes. Calculate i) the total work done by friction, ii) average**

**torque exerted by the force of friction and iii) the angular momentum of the wheel 2.0**

**minutes before it stops rotating. (10) **

**8. A steel ball A of mass 20.0 kg moving with a speed of 2.0 ms−1**

**collides with another**

**ball B of mass 10.0 kg which is initially at rest. After the collision A moves off with a**

**speed of 1.0 ms−1**

**at an angle of 30º with its original direction of motion. Determine the**

**final velocity of B. (10)**

**9. A satellite moves in an elliptical orbit with the Earth at one focus. At the perigee its**

**speed is v and its distance from the centre of the Earth is R . If the eccentricity of its**

**orbit is 0.5, calculate its speed at the apogee. (10)**

**10. a) A girl with a mass of 45 kg is standing on a scale in a lift. What is the weight of the**

**girl when (i) the lift is accelerating upwards at 2.0 ms s ****−2**

**and (ii) the lift is moving**

**down with a constant velocity. Calculate the inertial force in each case. (5)**

**b) An object is being rotated in a centrifuge which has a radius of 6.0 m. If the**

**acceleration of the centrifuge is 3 g, calculate the velocity of object and the time**

**period of its motion. (5)**

**LAST OF IGNOU BPHE-101 SOLVED ASSIGNMENT 2019 SUBMISSION – 30 SEPTEMBER 2019**

**IGNOU BPHE-101 SOLVED ASSIGNMENT 2019 PASSING MARKS – 40**