IGCSE PHYSICS ONLINE CLASS

IGCSE PHYSICS ONLINE CLASS

QUESTIONS

1 A car accelerates from rest at time t = 0 to its maximum speed.

Fig. 1.1 is the speed-time graph for the first 25 s of its motion.

1(a)(i)

(a) The mass of the car is 2300 kg.

For the time between t = 0 and t = 5.0 s, determine:

(i)  the acceleration of the car

 

 acceleration =............................... [2]

1(a)(ii)

(i) the resultant force acting on the car.

 resultant force = .................................... [2]

1(b)

(b) Describe the motion of the car between t = 10 s and t = 15 s. Explain how Fig. 1.1 shows this.

.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. [3]

1(c)

(c) Between t = 10 s and t = 15 s, the force exerted on the car due to the engine remains constant.

Suggest and explain why the car moves in the way shown by Fig. 1.1.

................................................................................................................................................................................................................................................................................................................................................................................................................................................... [2]

[Total: 9]

1(a)(i)

 $a=\frac{\Delta v}{\Delta t}or\ a=\frac{\left(v-u\right)}{t}$   in any form words, symbols or numbers or  $\left(a=\right)\ \frac{\Delta v}{\Delta t}or\ \left(a=\right)\ \frac{\left(v-u\right)}{t}$    or  $\frac{15\left(-0\right)}{5.0}\ or\ \left(a=\right)\ gradient$    C1
 $3.0\ ms^{-2}$                                                    A1

1(a)(ii)

(F =) ma in any form words, symbols or numbers or (F =) ma or  $2300\times3.0$     C1
 $6900\ N$                                                   A1

1(b) and 1(c)

1(b) accelerating or speed / velocity increasing                                 B1

at a decreasing rate or acceleration decreasing                                   B1

gradient (of graph is positive and) decreasing                                     B1

1(c) air resistance or friction mentioned or resistive force                 B1

air resistance or friction or resistive force increases (with speed)      B1

2(a)

2 (a) State two properties of an object that may be changed by the action of forces.

1...............................................................................................................................................

2...............................................................................................................................................[2]

2(b)

(b) A chest expander is a piece of equipment used by athletes in a gym. Fig. 2.1 shows a chest expander that consists of five identical springs connected in parallel between two handles.

2(b)(i)

Each spring has an unstretched length of 0.63 m.

Two athletes are stretching the chest expander by pulling on the two handles in opposite

directions.

(i) The springs obey Hooke’s law.

Explain what is meant by this statement.

........................................................................................................................................................................................................................................................................................................................................................................................................................... [2]

2(b)(ii)

(ii) Each athlete pulls the handle towards himself with a force of 1300 N.

1.   State the tension in each spring.

 

tension = ........................................................ [1]

    2. The chest expander stretches and each spring is now 0.94 m long.

Calculate the spring constant k of each spring.

k = ........................................................ [2]

2(b)(iii)

(iii) State the energy changes taking place as the two athletes use their muscles to stretch

the chest expander.

........................................................................................................................................................................................................................................................................................................................................................................................................................... [2]

[Total: 9]

2(a)

2(a) any two from:

shape

size / volume / length / density / any linear dimension

direction (of motion) / speed / velocity / momentum / kinetic energy / acceleration                                            B2

2(b)(i) and 2(b)(ii)

2(b)(i) extension and tension / force / load mentioned                      C1

extension is directly proportional to tension / force / load                 A1

2(b)(ii)1. 260 N                                                                                    B1

2(b)(ii)2

2(b)(ii)2.  $k=\frac{F}{x}$   in any form words, symbols or numbers or  $\left(k=\right)\ \frac{F}{x}$  or  260 / (0.94 – 0.63) or 260 / 0.31                                                     C1
840 N / m                                                                                          A1
2(b)(iii) from chemical (potential energy)                                         B1
to elastic (potential) / strain (at end)                                                 B1

2(b)(i) extension and tension / force / load mentioned                      C1
extension is directly proportional to tension / force / load                                            A1
2(b)(ii)1.  $260\ N$                               B1