9702/Oct Nov/11/2016/Q11

A car has mass m. A person needs to push the car with force F in order to give the car
acceleration a. The person needs to push the car with force 2F in order to give the car
acceleration 3a.

Which expression gives the constant resistive force opposing the motion of the car?

A ma
B 2ma
C 3ma
D 4ma

Solution:

Answer: A

Resultant force = applied force – resistive force

Ma = F- R

R = F- ma —-i

3ma = 2F – R

R = 2F – 3ma —–ii

Substitute for R in eq i

2F – 3ma = F – ma

F = 2ma

Therefore, R = 2ma – ma = ma

Resistive force = ma (A is the correct option)

Reference: PYQ - Oct/Nov 2016 Paper 11 Q11

9702/Oct Nov/11/2016/Q24

The diagram shows an experiment to produce a stationary wave in an air column. A tuning fork,

placed above the column, vibrates and produces a sound wave. The length of the air column can

be varied by altering the volume of the water in the tube.

The tube is filled and then water is allowed to run out of it. The first two stationary waves occur

when the air column lengths are 0.14 m and 0.42 m.

What is the wavelength of the sound wave?

A 0.14 m 

B 0.28 m 

C 0.42 m 

D 0.56 m

Solution:
Answer: D

From the figure of first two stationary waves occur when the air column lengths are 0.14m and 0.42m, we can conclude that

½ wavelength = 0.42 – 0.14

    wavelength = 2 (0.28)

                        = 0.56 m

Reference: PYQ - Oct/Nov 2016 Paper 11 Q24

9702/Oct Nov/11/2016/Q6

Question 6

A cyclist pedals along a raised horizontal track. At the end of the track, he travels horizontally into

the air and onto a track that is vertically 2.0 m lower.

The cyclist travels a horizontal distance of 6.0 m in the air. Air resistance is negligible.

What is the horizontal velocity v of the cyclist at the end of the higher track?

A      6.3 ms^–1 

B      9.4 ms^–1 

C      9.9 ms^–1 

D      15 ms^–1

Solution:

There are important points to note in this question:

The horizontal velocity v is used to calculate the horizontal distance

The time to reach the maximum height is the time to travel the horizontal distance

At maximum height u = 0

Using H = ut + 1/2gt^2

2 = 0 + 1/2×9.81xt^2

(t=0.6395s)

Horizontal distance = horizontal velocity(v) x time(t)

6 = 0.6395v

V = 9.4ms^-2 (B is the correct option)

Ans: B

Reference PYQ - Oct/Nov 2016 Paper 11 Q6