Question

A body of mass 1.5kg is thrown vertically upwards with an initial velocity of 15 m/s. What will be its potential energy at the end of 2s? (Take g= 10 m/s 2 )

Answer 1

Answer

• Kinetic Energy of the body is 150 J

Explanation

Given

• Mass = 1.5 kg
• It is thrown upwards with an initial velocity of 15 m/s
• Time = 2s
• Acceleration = -10 m/s²

To Find

• The Potential energy?

Solution

★ Using second Equation of motion

➝ s = ut+½at²

• u = Initial Velocity = 15 m/s
• t = Time = 2 sec
• a = Acceleration = -10 m/s²

Substituting the values,

➝ s = 15×2 + ½ × (-10) × 2²

➝ s = 30 + ½ × (-10) × 4

➝ s = 30 + (-10 × 2)

➝ s = 30 + (-20)

➝ Distance = 10 m

Kinetic Energy

➝ Kinetic Energy = mgh

• Mass = 1.5 kg
• Gravitational acceleration = 10 m/s²
• Height = 10 m

Substituting the values,

➝ Kinetic Energy = 1.5 × 10 × 10

➝ Kinetic Energy = 15 × 10

➝ Kinetic Energy = 150 J

Answer 2

$\bf \huge \star \ \pink q \pink u \pink e \pink stion$

A body of mass 1.5kg is thrown vertically upwards with an initial velocity of 15 m/s. What will be its potential energy at the end of 2s? (Take g= 10 m/s 2 )

$\bf \huge \star \ \pink s \pink o\pink l \pink ution$

.

To find the potential energy at the end of 2 sec, first we have to find the height which the body attains in 2 sec.

Using the equation, S=ut+1/2 at2

Given,

Initial velocity (u) = 15m/sec,

Acceleration (a), g in this question =10, time (t) = 2 sec

So, Height H = 15×2-1/2×10× (2)2

(Acceleration here is -g, because the body is moving upwards)

• 30-20= 10 m

So, in 2 sec the body will be at the height of 10 m

• At this height the potential energy is = mgh

• Here, m= mass= 1.5 kg, g=10, H= 10m

• So, P.E. = mgh = 1.5×10×10

$\large \green \{ \: \: = 150 Joule \: \ \green \}$