Ch- 4 Force and pressure
Answers
Answer:
3rd roman
a. Balanced and unbalanced forces:
*BALANCED FORCES :
If two individual forces are of equal magnitude and opposite direction, then the forces are said to be balanced forces.
Ex:hanging objects, standing on ground etc.
*UNBALANCED FORCES :
A force where two forces acting in opposing directions on a body, and are not equal in magnitude and size are called unbalanced forces.
Section D:
1. a)The finger exerts the force on the lemon
b) Gravity exerts force on swimmer and pulls him down.
c) The labourer exerts a force on the cart
d) Friction on the road provides the force on the tyres of the car.
e) The athlete exerts force on the ground to make the jump.
2. No , it is not possible for the object to move in a straight line with constant velocity when it experiences non-zero force.
- If the force is along the direction of Velocity , then the object will change its speed.
- If the force is perpendicular to the velocity, it will change its trajectory.
3. a) Balanced force: It is a force which experiences an equal and opposite force , such that their net effect is nullified and the object doesn't get accelerated.
Unbalanced Force: It is a type of force , which doesn't experience any force in the opposite direction. Hence , it provides net acceleration to an object.
b) Contact force: It is a type of force which acts on a body while it's in contact with the body; e.g. Friction.
Non-Contact force: This type of forces exert this action on a body from a distance , e.g Magnetic force , etc.
4. The speed of a ball going upwards decreases because the acceleration due to gravity is downwards and opposite to that of Velocity vector. Finally the ball comes to rest at max Height.
5. a) Gravitational force is responsible for his downward motion. It is a Non-Contact force.
b) If the man was without a parachute, then he would have fallen with a much higher speed because the parachute provides a retarding force.
6. a) If the area is doubled, but thrust remains same , then pressure becomes halved , because P = F/(Area).
b) If the thrust doubles , keeping the area constant , then the pressure becomes doubled.
7. The diver will experience higher pressure at a depth of 200 cm below water surface because he has higher Column of water above his head.
Pressure = rho × g × h