Work Energy

A body is moved along a straight line by a machine

A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time t is proportional to

t^1/2
t^1/4
t^3/2
t^3/4

If a body looses half of its velocity on penetrating 3 cm

If a body looses half of its velocity on penetrating 3 cm in a wooden block, then how much will it penetrate more before coming to rest?

1 cm
2 cm
3 cm
4 cm

From a building two balls A and B are thrown such that

From a building two balls A and B are thrown such that A is thrown upwards A and B downwards (both vertically). If v_A and v_B are their respective velocities on reaching the ground, then

their velocities depend on their masses
V_B > V_A
V_A = V_B
V_A > V_B

A spring of force constant 800 N/m has an extension of 5 cm

A spring of force constant 800 N/m has an extension of 5 cm. The work done is extending it from 5 cm to 15 cm is

32 J
8 J
24 J
16 J

A ball whose kinetic energy is E, is projected at an angle of 45° to the horizontal

A ball whose kinetic energy is E, is projected at an angle of 45° to the horizontal. The kinetic energy of the ball at the highest point of its flight will be

0
E
E/2
E/√2

A block of mass m=0.1 kg is connected to a spring of unknown spring constant k

A block of mass m=0.1 kg is connected to a spring of unknown spring constant k. It is compressed to a distance x from its equilibrium position and released from rest. After approaching half the distance (x/2) from equilibrium position, it hits another block and comes to rest momentarily, while the other block moves with a velocity 3 ms^-1. The total initial energy of the spring is:

1.5 J
0.6 J
0.3 J
0.8 J

A person trying to lose weight by burning fat lifts a mass of 10 kg

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies 3.8×10⁷ J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. Take g = 9.8 ms^-2

6.45 × 10^-3 kg
9.89 × 10^-3 kg
12.89 × 10^-3 kg
2.45 × 10^-3 kg