How to solve questions on Kinematics and deformation of solids
How to solve questions on Kinematics and deformation of solids
Question 1
A train with an initial velocity of 20ms-1 is subjected to a uniform deceleration of 2ms-2. The time required to bring the train to a complete halt is
A. 40s B. 5s C. 10s D. 20s
Solution
initial velocity = 20 ms-1
final velocity = 0 ms-1 ( since the train completely come to a halt)
deceleration = 2ms-1
V = u + at
0 = 20 + (-2) * t
-20 = -2t
t = 20/2 = 10 s
C is the correct option
Question 2
Calculate the work done, when a force of 20N stretches a spring by 50mm.
A. 2.5 J B. 0.5 J C. 1.5 J D. 2.0 J
Solution
workdone = 1/2 f e
f = 20 N
e = 50 mm = 0.05 m
workdone = 1/2 * 20 * 0.05 = 0.5 J
B is the correct option
Question 3 and 4 are from UTME 2012 Physics Questions – Type Yellow
Question 3
A car starts from rest and moves with a uniform acceleration of 30ms-2 for 20s. Calculate the distance covered at
the end of the motion.
A. 6km B. 12km C. 18km D. 24km.
Solution
initial velocity = 0 ms-1 ( since it is starting from rest)
acceleration = 30 ms-1
time taken = 20 s
using
s = ut + 1/2at^2
s =0 + 1/2 * 30 * 20^2
s = 400*15
s = 6000 m = 6 km
A is the correct option
Question 4
If a load of 1kg stretches a cord by 1.2cm, what is the force constant of
the cord?
A. 866 Nm-1 B. 833 Nm-1 C. 769 Nm-1 D. 667 Nm-1
Solution
Mass = 1kg
weight = mg = 1 * 10 = 10 N
extension = 1.2 cm = 0.012 m
force constant = f / e
k = 10 / 0.012
k = 833 Nm-1
B is the correct option
Question 5
This question is from advance physics Nelkon and parker
A car moving with a velocity of 36 kmh-1 accelerates uniformly at 1 ms-2 until it reaches a velocity of 54 kmh-1. Calculate
i the time taken
ii the distance travelled during the acceleration
Solution
x kmh-1 to ms-1 = (x *1000) / 3600
36 kmh-1 = (36 * 1000) / 3600 = 10 ms-1
54 kmh-1 = (54 * 1000) / 3600 = 15 ms-1
initial velocity = 10 ms-1
final velocity = 15 ms-1
v = u + at
15 = 10 + 1t
t = 15 – 10
t = 5 s
ii
v^2 = u^2 + 2as
15^2 = 10^2 + 2*1*s
225 = 100 + 2s
2s = 225 – 100
2s = 125
s = 62.5 m
Recommended: Short note on Kinematics
