Forces and Equilibrium

1.

Multiple Choice

30 sec

1 pt

State the principle of moments

A When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the same pivot.

B When a system is in equilibrium, the sum of the total clockwise moment is greater the sum of the total anti-clockwise moment about the same pivot.

C When a system is in equilibrium, the sum of the total clockwise moment is less than the sum of the total anti-clockwise moment about the same pivot.

D When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the different pivot.

2.

Multiple Choice

30 sec

1 pt

The figure below shows a man lifting a heavy rock using a steel bar. He pushes downwards on the end of the bar with a force F. Which pivot positions allows the force F to be as small as possible?

3.

Multiple Choice

15 mins

1 pt

What is the anticlockwise moment acting on this crane?

80,000Nm

100,000Nm

120,000Nm

140,000Nm

4.

Multiple Choice

30 sec

1 pt

Two masses of mass 10.0 and 6.0 kg are hung from massless strings at the end of a light rod. The rod is virtually weightless. A pivot (fulcrum) is placed off center and the system is free to rotate. If the 6.0 kg mass is 4.0 m away from the pivot, how far away is the 10.0 kg mass if the system is not rotating?

0.42 m

2.4 m

4.8 m

4.2 m

5.

Multiple Choice

5 mins

1 pt

Assuming the system is in equilibrium, calculate the missing distance d

3.4 m

2.8 m

4.4 m

1.6 m

6.

Multiple Choice

2 mins

1 pt

A boy of weight 600N sits on the see-saw as shown at a distance of 1.5m from the pivot. What is the force F required at the other end to balance the see-saw?

450 N

350 N

4.5 N

200 N

7.

Multiple Choice

30 sec

1 pt

What is the size of the moment shown by the black arrow?

30 Nm

36 Nm

40 Nm

60 Nm

8.

Multiple Choice

30 sec

1 pt

What to we call forces applied to anything that turns?

Minute

Moment

Minimum

Monument

9.

Multiple Choice

1 min

1 pt

What sense does the vector have?

down and right

up and left

up and right

down and left

10.

Multiple Choice

1 min

1 pt

What is the resultant vector's force?

10

20

-10

14.14

11.

Multiple Choice

30 sec

1 pt

why is the car on the left unstable?

Its centre of mass is high

it has a narrow base

it has a high height

all of the above

12.

Multiple Select

30 sec

1 pt

A heavy truck on wheels has a platform to attach to it. A man stands on the platform. The truck does not fall over.

Which position A, B, C, or D could be the centre of mass of the whole system (truck, platform and man) ?

A

B

C

D

13.

Multiple Choice

30 sec

1 pt

A plane lamina with centre of mass X touches the ground at point P. Which diagram shows the lamina in equilibrium?

14.

Multiple Select

30 sec

1 pt

B

A

B

C

D

15.

Multiple Choice

30 sec

1 pt

A

B

C

D

16.

Multiple Select

30 sec

1 pt

A

B

C

D

17.

Multiple Select

30 sec

1 pt

How many of these models will fall over?

1

2

3

4

All of the models

18.

Multiple Choice

30 sec

1 pt

Center of gravity is usually located where

more weight is concentrated

less weight is concentrated

less mass is concentrated

more mass is concentrated

19.

Multiple Choice

30 sec

1 pt

Where will be the centre of gravity of a uniform rod lies ?

At its end

At its middle point

At its centre of its cross sectional area

Depends upon its material

20.

Multiple Choice

30 sec

1 pt

A simple method to find centre of gravity of a body is usage of

stop watch

plumbline

pendulum

gauge

21.

Multiple Choice

30 sec

1 pt

Where do you hang the plumb line when determining the CG?

It doesn't matter, because it always goes through the CG

Only from the corners

From the point where you are suspending the object

At the right angle

22.

Multiple Choice

30 sec

1 pt

What is the centre of gravity

The centre of the earth

An imaginary point at which weight is concentrated

Gravity

How objects fall to the ground.

23.

Multiple Choice

30 sec

1 pt

Do all objects have a centre of gravity?

No objects have a centre of gravity

Only some objects have a centre of gravity

Only very heavy objects have a centre of gravity

Yes all objects have a centre of gravity

24.

Multiple Choice

15 mins

1 pt

Two forces are acting on it as shown.

What is the net force acting on the plane?

8,000 N to the right.

8,000 N to the left.

13,000 N to the right.

13,000 N to the left.

25.

Multiple Choice

3 mins

1 pt

A 2 kg falling object encounters 4-N of air resistance. The acceleration of the object is

-2 m/s²

2 m/s²

8 m/s²

16 m/s²

-8 m/s²

26.

Multiple Choice

15 mins

1 pt

The free body diagram of four boxes are shown below. Which box is in equilibrium?

27.

Multiple Choice

15 mins

1 pt

Who wins the tug of war with what net force?

The person on the left with 20 N

The person on the left with 80 N

The people on the right with 20 N

The people on the right with 100 N

28.

Multiple Choice

30 sec

1 pt

If an object is resting on a flat, horizontal surface, which of the following will be equal?

weight, mass

normal force, gravitational force

normal force, frictional force

gravitational force, frictional force

29.

Multiple Choice

30 sec

1 pt

The diagram shows a box being pulled up the ramp. Which letter represents normal force?

A

B

C

D

30.

Multiple Choice

3 mins

1 pt

Two soccer players kick a 200 g ball at the same time. One kicks it to the right with 150-N of force while the other kicks it to the left with 225-N of force. What is the acceleration of the ball?

375 m/s² to the right

375 m/s² to the left

0.375 m/s² to the right

0.375 m/s² to the left

31.

Multiple Choice

30 sec

1 pt

Suzie holds an apple at rest in her outstretched hand. The force she applies in holding it still...

equals the weight of the apple.

is slightly more than the weight of the apple.

is slightly less than the weight of the apple.

is zero, until she drops the apple.

32.

Multiple Choice

30 sec

1 pt

Burl and Paul have combined weights of 1300 N. The tensions in the supporting ropes that support the scaffold they stand on adds to 1700 N. What is the weight of the scaffold itself?

400 N

1300 N

1700 N

3000 N

33.

Multiple Choice

1 min

1 pt

Which one needs a greater net force to move, a kilogram of feathers or a kilogram of iron?

feathers

iron

same

depends on their friction

34.

Multiple Choice

2 mins

1 pt

After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals

twice the force with which it was fired

the same amount of force with which it was fired

1/2 the force with which it was fired

zero, since no force is requires to keep it moving.

35.

Multiple Choice

3 mins

1 pt

A 100 cm uniform rod weighs 10 N and is pivoted at A as shown in the diagram.

What is the weight of object W if the reading on the spring balance is 19 N?

19.0 N

20.0 N

27.1 N

63.3 N

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