9702/Oct Nov/13/2015/Q11

Question 11

A rocket of mass 30 000 kg sits on a launch pad on the Earth’s surface. The rocket motors
provide an upward force of 330 kN on the rocket.

What is the initial acceleration of the rocket?

A     0.12 m s^–2
B     1.1 m s^–2
C     1.2 m s^–2
D     11 m s^–2

Solution:
30 000kg x 9.81 = 294 300N
330 000 - 294 300 = 35700N
ma = 35700N
a = 35700/30000
   = 1.19
   = 1.2 ms^-2

Ans: C

Reference: PYQ - Oct/Nov 2015 Paper 13 Q11

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