Name: Motion With Variable Acceleration
Uploaded: 2019-07-19
Duration: 10 min 54 s
Description: You may be aware of the SUVAT equation, but do you think this can be applicable for all types of motion? No, what are those motion? Watch this to find out.

Question

A motorboat going downstream overcomes a raft (a wooden block) at a point

A; τ = 60 \min

. Later it turns back and after some time passes the boat and meets the raft at a distance

6.0 km

from the point

A

. Find the flow velocity assuming the duty of the engine to be constant.

Accepted Answer

Here, we can see from the diagram that both motorboat and the raft start moving from point $A$ in the direction of river flow. After reaching point $B$ , the motorboat turns and starts moving in the upstream direction. It meets with raft at point $C$ . It is given that the distance $6.0 km$ is equal to $6 km$ .

Suppose the velocity of motorboat with respect to the flow of river is $v$ and the flow velocity is $u$ . The velocity of the raft is equal to the velocity of flow since it is simply with the flow of river.

The distance travelled by the raft with respect to the wooden block in $60 \min$ or $1 hr$ ,
$s_{1} = ({\vec{v}}_{\frac{mb}{g}} - {\vec{v}}_{raft}) τ = [({\vec{v}}_{\frac{mb}{w}} + {\vec{v}}_{w}) - {\vec{v}}_{w}] τ$ ,

$\Rightarrow s_{1} = [(v + u) - u] τ = v τ = v km$ .

The distance travelled by the raft in that time, $(s_{2}) = u km$ .

After turning back, the boat has to travel $6.0 km$ distance with respect to the raft in order to reach the raft.
Hence, time, $τ_{1} = \frac{v}{v} = 1 hr$ .
The distance travelled by the raft in time $τ_{1}, (s_{3}) = u τ_{1} = u km$ .

It is given that, $A B = s_{2} + s_{3} = 6 km$ ,
$\Rightarrow u + u = 6 \Rightarrow u = 3 km h^{- 1}$

A motorboat going downstream overcomes a raft (a wooden block) at a point $A; τ = 60 \min$ . Later it turns back and after some time passes the boat and meets the raft at a distance $6.0 km$ from the point $A$ . Find the flow velocity assuming the duty of the engine to be constant.

Important Questions on Kinematics

Learn and Prepare for any exam you want !

A motorboat going downstream overcomes a raft (a wooden block) at a point A; τ=60 min. Later it turns back and after some time passes the boat and meets the raft at a distance 6.0 km from the point A. Find the flow velocity assuming the duty of the engine to be constant.

Important Questions on Kinematics

Learn and Prepare for any exam you want !

A motorboat going downstream overcomes a raft (a wooden block) at a point $A; τ = 60 \min$ . Later it turns back and after some time passes the boat and meets the raft at a distance $6.0 km$ from the point $A$ . Find the flow velocity assuming the duty of the engine to be constant.