Advertisements
Advertisements
प्रश्न
Find the average frictional force needed to stop a car weighing 500 kg at a distance of 25 m if the initial speed is 72 km/h.
Advertisements
उत्तर
\[\text{ Given } : \]
\[\text{ Mass of the car, m = 500 kg } \]
\[\text{ Distance covered by the car, s = 25 m }\]
\[\text{ Initial speed of the car, u = 72 km/h = 20 m/s } \]
\[\text{ Final speed of the car, } \nu = \text{ 0 m/s } \]
Retardation of the car,
\[a = \frac{\left( \nu^2 - u^2 \right)}{2s}\]
\[ \Rightarrow a = - \frac{400}{50} = - 8 \text{ m/ s}^2 \]
\[\text{ Frictional force, F = ma } = 500 \times 8 = 4000 N\]
APPEARS IN
संबंधित प्रश्न
A lawyer alleges in court that the police had forced his client to issue a statement of confession. What kind of force is this ?
List all the forces acting on (a) the pulley A, (b) the boy and (c) the block C in figure.
The sum of all electromagnetic forces between different particles of a system of charged particles is zero
A monkey is sitting on a tree limb. The limb exerts a normal force of 48 N and a frictional force of 20 N. Find the magnitude of the total force exerted by the limb on the monkey.
A body builder exerts a force of 150 N against a bullworker and compresses it by 20 cm. Calculate the spring constant of the spring in the bullworker.
The magnetic force on a charged particle is always perpendicular to its velocity. Can the magnetic force change the velocity of the particles? Speed of the particle?
The work done by all the forces (external and internal) on a system equals the change in ______.
A block of mass m slides down a smooth vertical circular track. During the motion, the block is in
No work is done by a force on an object if
(a) the force is always perpendicular to its velocity
(b) the force is always perpendicular to its acceleration
(c) the object is stationary but the point of application of the force moves on the object
(d) the object moves in such a way that the point of application of the force remains fixed.
A block of mass 250 g slides down an incline of inclination 37° with uniform speed. Find the work done against friction as the block slides through 1m.
A block of weight 100 N is slowly moved up a smooth incline of inclination 37° by a person. Calculate the work done by the person in moving the block through a distance of 2 m, if the driving force is (a) parallel to the incline and (b) in the horizontal direction.
A particle of mass m moves on a straight line with its velocity varying with the distance travelled, according to the equation \[\nu = a\sqrt{x}\] , where a is a constant. Find the total work done by all the forces during a displacement from \[x = 0 \text{ to } x - d\] .
A block of mass 2 kg kept at rest on an inclined plane of inclination 37° is pulled up the plane by applying a constant force of 20 N parallel to the incline. The force acts for one second. Show that the work done by the applied force does not exceed 40 J.
A block of mass 2 kg kept at rest on an inclined plane of inclination 37° is pulled up the plane by applying a constant force of 20 N parallel to the incline. The force acts for one second. Find the kinetic energy of the block at the instant the force ceases to act. Take g = 10 m/s2.
The 200 m free-style women's swimming gold medal at Seoul Olympics in 1988 was won by Heike Friendrich of East Germany when she set a new Olympic record of 1 minute and 57⋅56 seconds. Assume that she covered most of the distance with a uniform speed and had to exert 460 W to maintain her speed. Calculate the average force of resistance offered by the water during the swim.
A uniform chain of mass m and length l overhangs a table with its two third part on the table. Find the work to be done by a person to put the hanging part back on the table.
A lawn roller is pulled along a horizontal surface through a distance of 20 m by a rope with a force of 200 N. If the rope makes an angle of 60° with the vertical while pulling, the amount of work done by the pulling force is:
A bicyclist comes to a skidding stop in 10 m. During this process, the force on the bicycle due to the road is 200 N and is directly opposed to the motion. The work done by the cycle on the road is ______.
A body is being raised to a height h from the surface of earth. What is the sign of work done by applied force?
