The speed of the 8 . 0 kg mass in position A in the diagram is 6 . 0 ms - 1 . By the time it gets to B the speed is measured to be 12 . 0 ms - 1 . Estimate the frictional force opposing the motion. (The frictional force is acting along the plane.)

Total energy of the object at the position A = E A = m g h + 1 2 m v A 2 . (Here, v A is the speed of the object at position A ) ∴ E A = ( 8 . 0 × 9 . 8 × 12 . 0 ) + 1 2 × 8 . 0 × 6 . 0 2 = 940 . 8 + 144 . 0 = 1084 . 8 J Total energy of the object at the position B = E B = 1 2 m v B 2 = 1 2 × 8 . 0 × 12 . 0 2 = 576 . 0 J Therefore, the loss of total mechanical energy = 1084 . 8 - 576 . 0 = 508 . 8 J Now, the displacement of the object = AB = h sin 30 = 12 0 . 5 = 24 m . Let, f is the frictional force on the object. Therefore, the work done against the frictional force = f × 24 . Now, we know that the loss of total mechanical energy si equal to the work done against friction force. Therefore, f × 24 = 508 . 8 . ⇒ f = 508 . 8 24 = 21 . 2 N . Therefore, the frictional force = 21 . 2 N .

MEDIUM

Diploma

IMPORTANT

Earn 100

A massless string has the same tension throughout its length. Suggest why.

Important Questions on Mechanics

MEDIUM

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 54

A mass of

3.0 kg

is acted upon by three forces of

4.0 N

6.0 N

and

9.0 N

and is in equilibrium. Convince yourself that these forces can indeed be in equilibrium. The 9.0 N force is suddenly removed. Determine the acceleration of the mass.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 55

A horizontal force of

24 N

pulls a body a distance of

5.0 m

along its direction. Calculate the work done by the force.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 56

A block slides along a rough table and is brought to rest after travelling a distance of

2.4 m

. A force of

3.2 N

opposes the motion. Calculate the work done by the opposing force.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 57

A block is pulled as shown in the diagram by a force making an angle of $20^{o}$ to the horizontal. Find the work done by the pulling force when its point of application has moved $15 m$ .

Question Image

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 58

A block of mass

2.0 kg

and an initial speed of

5.4 {ms}^{- 1}

slides on a rough horizontal surface and is eventually brought to rest after travelling a distance of

4.0 m

. Calculate the frictional force between the block and the surface.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 59

A spring of spring constant

k = 200 {Nm}^{- 1}

is slowly extended from an extension of

3.0 cm

to an extension of

5.0 cm

. Calculate the work done by the extending force.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 61

The speed of the $8.0 kg$ mass in position $A$ in the diagram is $6.0 {ms}^{- 1}$ . By the time it gets to $B$ the speed is measured to be $12.0 {ms}^{- 1}$ .

Question Image

Estimate the frictional force opposing the motion. (The frictional force is acting along the plane.)

MEDIUM

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 2 - Mechanics>Test yourself>Q 64

The engine of a car is developing a power of

90 kW

when it is moving on a horizontal road at a constant speed of

100 km h^{- 1}

. Estimate the total horizontal force opposing the motion of the car.

A massless string has the same tension throughout its length. Suggest why.

Important Questions on Mechanics

Learn and Prepare for any exam you want !