##### TMA

# TMA2/PHY101 – Elementary Mechanics, Heat and Properties of Matter

## TMA Quiz Questions

TMA: TMA2/PHY101

PHY101 – Elementary Mechanics, Heat and Properties of Matter

Mr. Ibanga Efiong (eibanga@noun.edu.ng )

1 The rope shown in the figure attached hereto is wound around a cylinder of of mass 4.0 kg, radius 10cm and

I=0020kgm2

I=0.020kgm2

, where

I

is the moment of inertia about an axis along the cylinder axis. If the cylinder rolls without slipping, what the linear acceleration of its centre of mass?

Click here to see exhibit

A. 6.7m/s2

B. 3.3m/s2

C. 11.2m/s2

D. 1.5m/s2

2 The frictional force between the block and the table is 20 N. If the moment of inertia of the wheel is

4.0kgm2

, find how long it will take the block to drop

60cm

after the system is released.

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A. 7.37 s

B. 1.34 s

C. 3.71 s

D. 4.22 s

3 The mass shown in the figure attached starts from rest and falls a distance h. Find the angular speed of the wheel in terms of the radius of the wheel and I, m and h.

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A. ω=(2mgI/mb2−h)1/2

B. ω=(2mgI/mb2+h)1/2

C. ω=(2mgh/mb2−I)1/2

D. ω=(2mgh/mb2+I)1/2

4 Find the equation for the simple harmonic motion shown

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A. y=0.08sin(0.40πt−0.40π)

m

B. y=0.06sin(0.80πt+0.40π)

m

C. y=0.08sin(0.40πt+0.40π)

m

D. y=0.06sin(0.80πt−0.40π)

m

5 For the simple harmonic shown, evaluate

y

at

t=1.35s

Click here to see exhibit

A. 0.034 m

B. 0.023 m

C. 0.047 m

D. 0.012 m

6 When a 30-g mass is hung from the end of a spring, the spring stretches 8.0 cm. The same spring with a mass of 200 g at at its end is stretched 5.0 cm, released and allowed to oscillate on a frictionless horizontal surface. Find the frequency of the oscillation.

A. 0.54 Hz

B. 0.68 Hz

C. 0.34 Hz

D. 9.5 Hz

7 The system shown is an example of the Atwood’s machine. What is the acceleration of the masses? Assume the the pulley is frictionless and the rope massless. Take

g=9.8m/s2

Click here to see exhibit

A. 4.2m/s2

B. 2.5m/s2

C. 9.8m/s2

D. 3.3m/s2

8 A boy intends to move an m-kg crate across the floor by applying a constant force P newtons on it.The coefficient of friction between the floor and the crate is

μ

. Which of these is the best option for his task?

A. Push the crate with P applied horizontally

B. Push the crate with P inclined at an angle above the horizontal

C. Pull the crate with P inclined at an angle above the horizontal

D. Pull the crate with P inclined an angle below the horizontal

9 A boat propelled so as to travel with a speed of 0.50m/s in still water, moves directly (in a straight line perpendicular to the banks of the river assumed to be straight) across a river that is 60m wide. The river flows with a speed of 0.30m/s. How long in seconds does it take the boat to cross the river?

A. 150

B. 120

C. 300

D. 200

10 Which of the follwing statements is correcct?

A. An object can have a constant velocity even though its speed is changing

B. An object can have a constant speed even though its velocty is changing

C. An object can have zero acceleration and eventually reverses its direction

D. An object can have constant velocity even though its acceleration is not zero

11 Which of these is NOT a statement of Newtonâ€™s law of universal gravitation?

A. gravitational force between two particles is attractive as well as repulsive

B. gravitational force acts along the line joining the two particles

C. gravitational force is directly proportional to the product of the masses of the particles

D. gravitational force is inversely proportional to the square of the distance of the particles apart

12 How large an average force is required to stop a 1400-kg car in 5.0 s if the crate’s initial speed is 25 m/s?

A. 2000 N

B. 3500 N

C. 9000 N

D. 7 000N

13 A 10-g bullet of unknown speed is shot horizontally into a 2-kg block of wood suspended from the ceiling by a cord. The bullet hits the block and becomes lodged in it. After the collision, the block and the bullet swing to a height 30cm above the original position. What was the speed of the bullet? (This device is called the ballistic pendulum). Take

g=9.8ms−2

A. 487 m/s

B. 640 m/s

C. 354 m/s

D. 700 m/s

14 A 40-g ball travelling to the right at 30 cm/s collides head on with an 80-g ball that is at rest. If the collision is perfectly elastic, find the velocity of each ball after collision

A. the first ball is going to the right at 10m/s while the other is going to the left at 20m/s

B. the first ball is going to the left at 10m/s while the other is going to the right at 20m/s

C. the first ball is going to the left at 20 m/s while the other is going to the right at 10 m/s

D. the first ball is going to the right at 10 m/s while the other is going to the left at 10 m/s

15 A gun of mass M is used to fire a bullet of mass m. The exit velocity of the bullet is v. Find the recoil velocity of the gun

A. Mv/m

B. mv/M

C. −Mv/m

D. −mv/M

16 A 30,000-kg truck travelling at 10.0m/s collides with a 1700-kg car travelling at 25m/s in the opposite direction. If they stick together after the collision, how fast and in what direction will they be moving?

A. 8.1 m/s in the direction of the truck’s motion

B. 12.3 m/s in the direction of the car’s motion

C. 24.2 m/s in the direction of the car’s motion

D. 17.6 m/s in the direction of the truck’s motion

17 Sand drops at the rate of 2000 kg/min. from the bottom of a hopper onto a belt conveyor moving horizontally at 250 m/min. Determine the force needed to drive the conveyor, neglecting friction.

A. 500 N

B. 800 N

C. 139 N

D. 152 N

18 The exhaust gas of a rocket is expelled at the rate of 1300 kg/s, at the velocity of 50 000 m/s. Find the thrust on the rocket in newtons

A. 6.5×107

B. 3.5×107

C. 7.6×107

D. 5.7×107

19 A force of

2i⃗ +7j⃗

N acts on a body of mass 5kg for 10 seconds. The body was initially moving with constant velocity of

i⃗ −2j⃗

m/s. Find the final velocity of the body in m/s, in vector form.

A. 5i⃗ +12j⃗

B. 12i⃗ −5j⃗

C. 10i⃗ −7j⃗

D. 7i⃗ +10j⃗

20 Two trolleys X and Y with momenta 20 Ns and 12 Ns respectively travel along a straight line in opposite directions before collision. After collision the directions of motion of both trolleys are reversed and the magnitude of the momentum of X is 2 Ns. What is the magnitude of the corresponding momentum of Y?

A. 6 Ns

B. 8 Ns

C. 10 Ns

D. 30 Ns

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