Exam questions, Physics paper 1

Question 1

A skier travels down a slope with a constant acceleration.

• Acceleration : 3 m/s ^ 2
• Speed at P : 7.6 m/s
• Speed at Q : 24 m/s
  a) what is the distance from P to Q?
  b) calculate the time taken for the skier to travel from P to Q.

Answer 1

a)
v^2 - u^2 = 2ax
24^2 - 7.6^2 = 2 * 3 * x
x = (24^2 - 7.6^2) / 6
x = 86 m

b)
a = (v - u) / t
3 = (24 - 7.6) / t
t = (24 - 7.6) / 3
t = 5.5 s

Question 2

A car travelling at 15 m/s comes to rest in a distance of 14 metres when the brakes are applied. Calculate the deceleration of the car.

Answer 2

a = (v^2 - u^2) / 2x
a = (-) 15^2 / 2 * 14
a = - 8.04

Question 3

An aircraft waits at the start of a runway. The aircraft accelerates from a speed of 0 m/s to a speed of 80 m/s. The acceleration of the aircraft is 4 m/s^2. Calculate the distance ,x, travelled by the aircraft while it is accelerating.

Answer 3

x = (v^2 - u^2) / 2a
x = (80^2 - 0^2) / 2 x 4
x = 800

Question 4

The symbol ‘g’ can be used to refer to the acceleration due to gravity (gravitational field strength) and has the unit of m/s^2. What is another unit for ‘g’.

Answer 4

N/kg

Question 5

Two students try to determine a value for g, the acceleration due to gravity (gravitational field strength) . They measure the time ,t, for a small steel ball to fall through a height ,h, from rest.

  t = 0.74 seconds
  h = 2.5 metres

Calculate a value for g

Answer 5

g = 2h / t^2
g = 5 / 0.5476
g = 9.13 m/s^2

Question 6

The mass of a car is 625 kg. Calculate its weight on earth.

Answer 6

w = mg
w = 625 * 10
w = 6250 N

Question 7

A toy car has a mass of 0.1 kg. The toy car accelerates at 2 m/s^2.Calculate the force producing this acceleration. State the unit.

Answer 7

F = m x a
F = 0.1 x 2
F = 0.2 N

Question 8

What is the aproximate radius of an atom

Answer 8

1 x 10 ^ -10 metres

Question 9

At 1pm the activity of a radioisotope is 700 counts per minute. By 4pm the activity has fallen to 175 counts per minute. Calculate the half-life of the radioisotope.

Answer 9

700 / 2 = 350
350 / 2 = 175

Between 1pm and 4pm (3 hours) there are two half lives. So 1 1/2 hours represents 1 half life.

Question 10

The initial activity of a radioactive source is 5860 Bq. Calculate the activity of the radioactive source after 3 half-lives. Give your answer as a percentage of the initial activity to two significant figures.

Answer 10

The radioactivity of a sample after 3 half lives is 0.5x 0.5x0.5 = 0.125 = 12.5%

Round up to two significant figures = 13%

Question 11

The initial activity of a radioactive sample is 3800 Bq. Calculate the percentage reduction in activity after two half-lives.

Answer 11

0.5 x 0.5 = 0.25
1 - 0.25 = 0.75
0.75 x 100 = 75%