Question

3.Observe the following V- graph of a body moving on a straight road and
answer the questions that follow. Mass of the body is 40 kg.
25-
B
20.-
Velocity
(X
15-
10
10.
A
B
8
10
12
Time (s)
i) What force acts on the body from 10 s to 12 s time interval and why?
ii) Calculate the force acting on the body from t=0s to t = 10s.
in which time interval does the retarding force act on the body?
iii) in which direction does frictional force act on a moving body?
iv) in which direction does frictional force act on a moving body ? ​

Answer 1

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Answer 2

1. During the time period t=10s to t=12s, 0 N force acts on the body.
2. During the time period t=0s to t=10s, 60N force acts on the body.
3. Frictional force always acts opposite to the direction of motion of the body.

Explanation 1:

If we look at the graph carefully,

During the time interval $t=10s$ to $t=12s$ , the velocity is constant. This means that no change is seen during the time period  or Δv = 0.

And we know, acceleration is the change in velocity with respect to time

$a=\frac{dv}{dt}=0$

Force on any object is given by $F= ma$   ;  $a=0m/s^{2}$

Hence, force during $AB$ will be $0N.$

Explanation 2

During, $t=0s$ to $t=10s$, we can see that the body has accelerated from

initial velocity $(u)=5m/s$  to final velocity $(v)=20m/s$ in $10s$.

Hence, the acceleration of the body is

$a=\frac{(20-5)}{10}$   $;$ $or$

$a=1.5m/s^{2}$

Force during this time period will be

$F= ma$

$F=(40)(1.5)=60N$

Hence, force acting on the body will be $60N.$

Explanation 3

Frictional force always acts opposite to the direction of the motion of body.

Although your question is incomplete, you might be referring to the diagram below.