Mechanics | Relativity Answers

Someone takes 15 minutes to walk up a hill 100m high.His weight is 600N.a)How much work did he do in climbing the hill?

B)what power is developed by his muscles as he climb s?

C)If he climbs up the hill,his muscles can exert 600watts.How long will it take him to getto the top of the hill.

three particles of the respective masses m1-12kg,m2-24kg, and m3-36kg formed an equilateral triangle of side length a=120cm.If we locate m1 at the origin of the xy-plane and put m2 to right of m1 at right axis.What is the approximate coordinate s of the center of the mass of the system?

In a Bangladesh-Australia cricket match, Sakib Al Hasan throws a ball towards the batsman. The ball starts to spin with 18.0 rev/s. The radius of the ball is 7.1cm. (a) Find the tangential speed of the outer periphery of the ball as it spins. (b) What is the centripetal acceleration of the cricket ball? (c) Let’s consider, due to air friction, the spin of the ball decays at the rate of 0.6 rev/s2 . Now find how long it will take for the ball to stop spinning and the total angle through which it will rotate during this time. (Consider the rate as constant)

1. The position of a particle which moves along the straight line is define by the relation 𝑥(𝑡) = 𝑡^3 − 6𝑡^2 − 15𝑡 + 40 where 𝑥 and 𝑡 are expressed in meters and seconds respectively. Note that the coefficients of t have dimensions accordingly. (a) Determine when the velocity of the particle is zero. (b) Calculate the position vector and distance travelled by the particle when the acceleration is zero. Consider that at the starting point time 𝑡 = 0 sec. (c) Does the particle move at constant velocity or constant acceleration? Justify your answer

Two forces, 3 N and 5 N respectively, act on the same point simultaneously. The magnitude of their resultant force is 2 N when the angle between them is _____.

Two crates with masses of 100 kg and 200 kg respectively are connected with a light inelastic rope. A force with magnitude F pulls the crates up an incline with an angle of 30° with the horizontal

The kinetic coefficient of friction for the 100 kg crate is 0,3 and that of the 200 kg crate is 0,5.

Calculate the Magnitude of F if the system moves at a constant velocity up the

incline.

Kelebogile and Thabiso want to move a crate in a classroom.

Kelebogile initially pulls the crate with a force of 80 N to the right and Thabiso pulls the crate with a force of 50 N to the left as shown in the diagram below. Ignore all effects of friction.

What is the net force exerted on the crate?

The earth exerts a gravitational force of 1,9 x 1020 N on the moon. The mass of the moon is 7,4 x 1022 kg and its radius is 1,74 x 106 m.

An astronomer that weighs 20 kg on earth, lands on the moon. What would his mass be on the moon?

The earth exerts a gravitational force of 1,9 x 1020 N on the moon. The mass of the moon is 7,4 x 1022 kg and its radius is 1,74 x 106 m.

Calculate the distance between the centres of the earth and the moon.

(MEarth = 6 x 1024 kg)

The earth exerts a gravitational force of 1,9 x 1020 N on the moon. The mass of the moon is 7,4 x 1022 kg and its radius is 1,74 x 106 m.

Calculate the magnitude of the gravitational acceleration on the moon