1. An object experiences a net zero external unbalanced force. Is it possible for the object
to be travelling with a non-zero elocity? If yes, state the conditions that must be
placed on the magnitude and direction of the velocity. If no, provide a reason.
2. When a carpet is beaten with a stick, dust comes out of it. Explain.
3. Why is it advised to tie any luggage kept on the roof of a bus with a rope?
4. A batsman hits a cricket ball which then rolls on a level ground. After covering a short
distance, the ball comes to rest. The ball slows to a stop because (a) the batsman did not hit
the ball hard enough. (b) velocity is proportional to the force exerted on the ball. (c) there is a
force on the ball opposing the motion. (d) there is no unbalanced force on the ball, so the ball
would want to come to rest.
5. A truck starts from rest and rolls down a hill with a constant acceleration. It travels a
distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if it's mass is 7
tonnes (Hint: 1 tonne = 1000 kg.)
6. A stone of 1 kg is thrown with a velocity of 20 ms across the frozen surface of a lake and
comes to rest after travelling a distance of 50 m. What is the force of friction between the
stone and the ice?
7. An automobile vehicle has a mass of 1500 kg. What must be the force between the vehicle
and road if the vehicle is to be stopped with a negative acceleration of 1.7 ms"?
8. Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a
constant velocity. What is the friction force that will be exerted on the cabinet?
Whoever answers all will get marked brainliest. Please do it quick!
Answers
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Answer:
When a net zero external unbalanced force is applied on the body, it is possible for the object to be travelling with a non-zero velocity. In fact, once an object comes into motion and there is a condition in which its motion is unopposed by any external force; the object will continue to remain in motion.
(2) If a carpet is beaten with a stick then the carpet begins to move. But, the particles of dust are trying to resist their state of rest. The dust particles remain in a state of rest, while the carpet moves, as per Newton's first law of motion. The particles of dust thus emerge from the carpet.
(3) If any luggage kept on the roof of the bus is not tied with a rope, then it tends to move forward due to its inertia. In this process, it could fall off the bus. Therfore, it is advised to tie any luggage kept on the roof of a bus with a rope.
(4) After covering a short distance, the ball comes to rest because there is frictional force on the ball opposing its motion. Frictional force always acts in the direction opposite to the direction of motion. Hence, this force is responsible for stopping the cricket ball.
(5) Given data:
Mass of stone(m)=7000 kg
Distance(S)=400 meter
Time(t)=20 second
1) We have to find the acceleration of the truck
So from the equation of motion S=ut+
2
1
a×t
2
, whereu=0
S=
2
1
a×t
2
a=
t
2
2×S
=
20×20
2×400
=2
sec
2
m
(6) Initial velocity of the stone, u= 20 m/s
Final velocity of the stone, v= 0
Distance covered by the stone, s= 50 m
We know the third equation of motion
v²=u²+2as
Substituting the known values in the above equation we get,
0² = (20)²+2(a)(50)
-400 = 100a
a = -400/100 = -4m/s² (retardation)
We know that
F = m×a
Substituting above obtained value of a=-4 in F= m x awe get,
F = 1×(-4) = -4N
(Here the negative sign indicates the opposing force which is Friction)
(7) What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7 m s2?. Hence, the force between the automobile and the road is ˆ'2550 N, in the direction opposite to the motion of the automobile.
(8) The cabinet will move with constant velocity only when the net force on it is zero. Therefore, force of friction on the cabinet = 200 N, in a direction opposite to the direction of motion of the cabinet.
Explanation: